Method and apparatus for measuring flow through a lumen

ABSTRACT

A prosthesis for monitoring a characteristic of flow includes a first tubular prosthesis having a lumen and a sensor for detecting the characteristic of flow through the lumen. The sensor may be covered with another tubular prosthesis or by a layer of material in order to insulate the sensor from the fluid flow. A pocket may be formed between the tubular prosthesis and the adjacent layer of material or prosthesis and the sensor may be disposed in the pocket.

CROSS-REFERENCE

The present application is a continuation of U.S. patent applicationSer. No. 14/163,991 (Attorney Docket No. 44167-703.201) filed Jan. 24,2014, now U.S. patent Ser. No. ______, which is a non-provisional of,and claims the benefit of U.S. Provisional Patent Application No.61/756,159 (Attorney Docket No. 44167-703.101) filed Jan. 24, 2013; theentire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Peripheral arterial disease (PAD) refers to the obstruction of arteriesother than those supplying the heart and within the brain. A commondenominator among pathologic processes is the impairment of circulationand resultant ischemia to the end organ involved. Without being bound byany particular theory, the following pathologies and their mechanisms ofaction are believed to be relevant. Atherosclerosis is the most commonpathology associated with PAD. It is a hardening of an arteryspecifically caused by an atheromatous plaque. Hyperlipidemia,hypercholesterolemia, hypertension, diabetes mellitus, and exposure toinfectious agents or toxins such as from cigarette smoking are allimportant and independent risk factors for atherosclerosis. The commonmechanism is thought to be endothelial cell injury, smooth muscle cellproliferation, inflammatory reactivity, and plaque deposition.

Several components are found in atherosclerotic plaque—lipids, smoothmuscle cells, connective tissue and inflammatory cells, oftenmacrophages. Lipid accumulation is central to the process anddistinguishes atheromas from other arteriopathies. In advanced plaques,calcification is seen and erosive areas or ulcerations can occur,exposing the contents of the plaque to circulating prothrombotic cells.In the event of plaque rupture the contents of the lipid core areexposed to circulating humoral factors, the body, perceiving theulceration as an injury, may lay down platelets and initiate clotformation.

Ischemia can result from a number of possible plaque behaviors, such asencroachment on the lumen (stenosis or narrowing) with hypoperfusion,stagnation, and thrombosis; rupture of the fibrous cap inducing thrombusformation in the lumen, with outright occlusion; and embolization ofthrombotic debris into the downstream circulation. There is aninterestingly predictable pattern of distribution of atheromatousplaques throughout the arterial tree that is likely a result ofconsistent hemodynamic stresses associated with human anatomic design.Atheromatous plaques tend to occur at bifurcations or at bendsassociated with repetitive external stresses. Areas of increased shearstress due to disturbances in flow or turbulence, with lateralizingvectors and eddy formation, are prone to atheromatous degeneration.

Due to the insidious nature of PAD and renal failure, 1.4 millionarterial bypass procedures are performed in the United States toalleviate the consequences of inadequate blood flow. Of these arterialbypass procedures, 450,000 utilize a synthetic vascular graft. Thenumber of total bypass procedures is increasing along with an agingpopulation. The percentage of bypass procedures which utilize asynthetic graft is also increasing due to the rising incidence ofdiabetes and obesity. After successful surgical placement, bypass graftsare at a high risk for failure from a number of factors. Factorspredisposing to graft failure include the progression of vasculardisease and promotion of clotting factors.

Synthetic graft placement can cause fibrosis due to intimal hyperplasiaand is a major cause of bypass graft failure. In an end-to-sideconfiguration of synthetic graft placement, abnormal shear stressconditions are thought to occur, contributing to the development ofintimal hyperplasia. Intimal hyperplasia is a physiologic healingresponse to injury to the blood vessel wall. When the vascularendothelium is injured, endothelial cells release inflammatory mediatorsthat trigger platelet aggregation, fibrin deposition and recruitment ofleukocytes to the area. These cells express growth factors that promotesmooth muscle cell migration from the media to the tunica intima. Thesmooth muscle cells proliferate in the intima and deposit extracellularmatrix, in a process analogous to scar formation.

The presence of prosthetic material in the vessel seems to acceleratethe development of intimal hyperplasia. Restenosis occurring 3 to 12months after intervention is typically due to intimal hyperplasia.Stenosis from intimal hyperplasia is often difficult to treat. Unlikesoft atheromatous plaques, these stenoses are firm and require prolongedhigh inflation pressures to dilate with a balloon. These stenoses oftenrecur; repeated dilatation causes repeated intimal injury andperpetuates the intimal healing response. While there have beensignificant advances in the field, such as, drug-eluting stents, drugcoated angioplasty balloons, systemic low-dose low molecular weightheparin, and systemic low-dose warfarin; the deleterious effects ofintimal hyperplasia have not been resolved.

Graft failure leads to disastrous consequences for the patient, such astissue ischemia and limb loss. Not infrequently, amputations in thevascular patients are prone to breakdown and then need for revision iscommon, thereby prolonging the patient's time in the hospital,lengthening the recovery process, decreasing the chances of functionalrecovery, and contributing to a high rate of depression. In addition tothe financial cost of treatment and lost wages, there is a significantcost to the patient in terms of decreased mobility, potential loss ofemployment and decreased quality of life.

Currently, vascular grafts are monitored after surgical placement byeither angiography or duplex ultrasonography. These tests are typicallyrepeated periodically, e.g., at six month intervals, since restenosisprecipitating graft failure is prevalent. Grayscale (B-mode) ultrasoundis employed to visualize the architecture of the graft. Color Dopplerultrasound visualizes the blood flow velocity (cm/s) or flow rate withinthe lumen. Severe calcification of the distal vessels or the vasculargraft can impede imaging of flow. Given the various physiologic factorsand outside influences (i.e. operator dependence) affecting the outcomeof these tests, it is difficult to quantitatively ascertain the resultsof the procedure with any degree of accuracy or precision. Due to theburdensome nature of this technique, the medical practitioner will onlyget two or three opportunities to characterize the patency of thevascular graft during the first year. It would therefore be advantageousto provide improved methods and devices for monitoring blood flowthrough the synthetic graft immediately following surgical implantationand thereafter, either periodically or on a continuous basis. At leastsome of these objective will be satisfied by the exemplary methods anddevices described below.

2. Description of the Background Art

References which may be related to measuring flow through a prosthesisinclude U.S. Pat. Nos. 8,216,434; 8,211,165; 8,211,166; 8,211,168;6,486,588; 7,785,912; 5,807,258; 7,650,185; 7,963,920; 8,016,875;5,967,986; 7,813,808; 6,458,086; 5,409,009; 5,598,841; 5,995,860;6,049,727; 6,173,197; 7,267,651; 6,682,480; 6,053,873; 5,522,394;7,488,345; 7,025,778; 7,922,667; 5,785,657; 7,949,394; 7,948,148;4,600,855; 5,411,551; 5,598,847; 7,918,800; 5,760,530; 4,920,794;8,308,794; 7,747,329; 7,572,228; 7,399,313; 7,261,733; 7,060,038;6,840,956; 6,416,474; 6,015,387; 5,967,986; 5,807,258; and US PatentPublication Nos. 2005/0210988; 2004/0082867; 2012/0058012; 2011/0054333;2008/0033527; 2005/0277839; 2002/0183628 and 2002/0183628.

SUMMARY OF THE INVENTION

The present invention generally relates to medical systems, devices andmethods, and more particularly relates to monitoring of flow through aprosthesis. More particularly, the present invention relates tomonitoring flow through a prosthetic vascular graft.

In a first aspect of the present invention, a prosthesis for monitoringa characteristic of flow comprises first and second tubular prosthesesand a sensor. The second tubular prosthesis has a lumen extendingtherethrough, and the first tubular prosthesis is disposed over thesecond tubular prosthesis thereby forming a pocket therebetween. Thesensor detects a characteristic of fluid flowing through the lumen ofthe second tubular prosthesis, and is disposed in the pocket. The sensoris also insulated from contact with fluid flowing through the lumen.

The prosthesis may be a prosthetic vascular graft, and the first or thesecond tubular prostheses may be a tubular prosthetic vascular graft, astent, or a stent-graft. The first tubular prosthesis or the secondtubular prosthesis may be formed primarily from polyethyleneterepthalate, polyester or ePTFE. The first tubular prosthesis may befixedly attached to the second tubular prosthesis, or the two may beintegral with one another. The two tubular prostheses may be discretefrom one another. The two tubular prostheses may be sintered, sutured,stapled or otherwise coupled to one another.

The first tubular prosthesis may have a first length and the secondtubular prosthesis may have a second length. The second length may besubstantially the same as the first length, or it may be shorter orlonger than the first length.

The sensor may comprise a piezoelectric sensor or a doppler sensor. Thesensor may detect thermal properties of the fluid flow, stress, strain,or pressure exerted on the first or the second tubular prosthesis by thefluid flow. The characteristic sensed by the sensor may comprisevelocity or flow rate of the fluid flow, or occlusion, degree ofocclusion, stenosis, or degree of stenosis in the lumen. The velocitymay be determined either directly or indirectly from the sensedcharacteristic.

The sensor may be disposed circumferentially around the first and/or thesecond tubular prosthesis. The first or the second tubular prosthesismay have a longitudinal axis and the sensor may be orthogonal to thelongitudinal axis. The sensor may comprise a plurality of sensorsdisposed circumferentially around the first and/or the second tubularprosthesis, or the sensor may comprise a plurality of discrete sensorscircumferentially disposed around the first and/or the second tubularprosthesis, and the plurality of discrete sensors may be disposed in acommon plane. The sensor may comprise a plurality of discrete sensorsdisposed axially along the first and/or the second tubular prosthesis.The plurality of discrete sensors may be disposed substantially parallelto a longitudinal axis of the first and/or the second tubularprosthesis. The sensor may comprise first and second annular bandscircumferentially disposed around the first and/or the second tubularprosthesis, and the first annular band may be axially separated from thesecond annular band. The first or the second annular band may form aclosed loop, or may be an open loop. The sensor may comprise a pluralityof elongated sensors, and the plurality of elongated sensors may beaxially oriented along the first and/or the second tubular prosthesis.

The sensor may be configured to capture a plurality of characteristicsof the fluid flow in the lumen. The sensor may comprise a plurality ofsensors that are disposed on the first and/or the second tubularprosthesis. The plurality of sensors may comprise a first sensor and asecond sensor. The first sensor may be configured to capture a firstcharacteristic of the fluid flow in the lumen, and the second sensor maybe configured to capture a second characteristic of the fluid flow inthe lumen. The first characteristic may be different than the secondcharacteristic. The first characteristic and the second characteristicmay be portions of a single signal.

The first sensor may be disposed in a first orientation relative to thefirst or the second tubular prosthesis, and the second sensor may bedisposed in a second orientation relative to the first or the secondtubular prosthesis. The first orientation may be different than thesecond orientation. The plurality of sensors may be helically disposedaround the first or the second tubular prosthesis. The first or thesecond tubular prosthesis may have a longitudinal axis, and the sensormay be disposed substantially parallel to the longitudinal axis, ortransverse thereto.

The sensor may comprise a plurality of undulating elongated elementsdisposed over the first and/or the second tubular prosthesis. The sensormay have a collapsed configuration sized for delivery of the sensor andan expanded configuration adapted to substantially match an anatomy inwhich the sensor is deployed. In the expanded configuration the sensormay form a closed annular band. The sensor may be disposedcircumferentially around the first or the second tubular prosthesis toform an open or a closed annular band therearound.

In another aspect of the present invention, a system for monitoring flowthrough a prosthesis comprises a prosthesis having a lumen extendingtherethrough and a sensor. The lumen is configured for fluid flowtherethrough, and the sensor is operatively coupled with the prosthesisand configured to sense a characteristic of the fluid flow and outputdata related to the fluid flow.

The system may further comprise a wireless transmitter for transmittingthe data from the sensor to a remote position. The system may alsocomprise a display device operatively coupled with the sensor and thatis configured to display the output data. Other elements of the systemmay include a processor or a power source. The processor may beconfigured to process the output data, and the power source may providethe power to the system. The power source may be a battery. The sensormay not require power to be actively supplied to thereto in order tosense the fluid flow and output the data related to the fluid flow. Thesystem may further comprise an integrated circuit chip operativelycoupled with the sensor. The integrated circuit chip may have aprocessor, or it may not contain a processor, or it may comprise a datatransmitter. The data transmitter may transmit the data using at leastone of radiofrequency, Bluetooth, internet, or near field communicationmeans.

The system may further comprise a receiver for receiving the data. Thereceiver may be an intracorporeal or extracorporeal device. The receivermay process the data prior to transmission of the data to a displaydevice that is configured to display the data to a physician or othercaregiver.

In yet another aspect of the present invention, a prosthesis formonitoring flow comprises a first tubular prosthesis having a lumentherethrough, a sensor coupled to the first tubular prosthesis, and alayer of material disposed over the sensor. The sensor is configured tosense fluid flow through the lumen, and the layer of material issealingly coupled to a surface of the first tubular prosthesis therebyencapsulating the sensor such that the sensor is insulated from contactwith fluid flowing through the lumen.

The first tubular prosthesis may be a prosthetic vascular graft and thefluid may be blood with the fluid flow being blood flow through theprosthesis. The first tubular prosthesis may be formed primarily frompolyethylene terepthalate, polyester, or ePTFE. The first tubularprosthesis may be a stent or a stent-graft.

The sensor may be coupled to an inner or outer surface of the firsttubular prosthesis. The layer of material may be a patch. The layer maybe sintered, adhesively coupled, sutured, or stapled to the firsttubular prosthesis.

In another aspect of the present invention, a method for monitoring flowthrough a prosthesis comprises providing a prosthesis having a lumentherethrough and a sensor coupled to the prosthesis, and coupling theprosthesis to a fluid path in a patient so that fluid flows through theprosthesis. The method also comprises sensing a characteristic of thefluid flow through the lumen with the sensor, transmitting datarepresentative of the sensed fluid flow to a receiver disposedextracorporeally relative to the patient, and outputting the data.

The prosthesis may be a vascular graft, a stent, or a stent-graft. Thefluid path may comprise a blood flow path. Transmitting the data maycomprise wirelessly transmitting the data. The method may furthercomprise reviewing the sensed data, determining whether flow through theprosthesis is adequate based on the sensed data, and performing ablockage clearing procedure on the prosthesis if the flow is inadequate.The blockage clearing procedure may comprise angioplasty, atherectomy oradministration of a thrombolytic agent.

The method may further comprise indicating the necessity of additionaldiagnostic testing of the prosthesis. The data may comprise an acousticsignal. The method may further comprise pairing the prosthesis with anexternal device.

Coupling may comprise forming an anastomosis between a proximal end or adistal end of the prosthesis and the fluid path. Coupling may comprisepositioning the prosthesis between a native vessel and another graft ora second native vessel. The coupling may comprise positioning theprosthesis between ends of a native vessel or coupling an end of theprosthesis to a side of a native vessel or native conduit. Coupling maycomprise slidably engaging the prosthesis over a native vessel oranother prosthesis.

The fluid flow may be blood flow, urine flow, cerebrospinal fluid flowor any other non-blood flow. Outputting the data may comprise sendingthe data to a bedside monitor that is optionally coupled to theInternet. The method may also comprise providing an enabled device thatinterrogates the prosthesis. The enabled device may comprise apacemaker, an implantable device, bedside monitor, a glucose meter, ablood pressure meter, a smart phone, a smart watch, or an Internetconnected device. The method may further comprise inductively providingpower to the prosthesis.

These and other embodiments are described in further detail in thefollowing description related to the appended drawing figures.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.In the event that references incorporated by reference containdisclosure that conflicts with disclosure in the present application,the present application controls.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 shows a prosthesis with two lumens and a sensor in between thetwo lumens.

FIG. 2 shows a prosthesis with two lumens with a sensor placed betweenthem in which the inner lumen is substantially shorter than the outerlumen.

FIG. 3 shows a prosthesis with two lumens with a sensor placed betweenthem in which the outer lumen is substantially shorter than the innerlumen.

FIG. 4 shows a prosthesis with two lumens in which one sensor is placedbetween the two lumens on the inner lumen, and one sensor is placed onthe outside of the outer lumen.

FIGS. 5A-5C show examples of a prosthesis with a plurality of sensorslocated on the outer wall of the inner lumen, on the outer wall of theouter lumen, and on a combination of those two cases which are disposedcircumferentially.

FIGS. 6A-6C show examples of a prosthesis with a plurality of sensorslocated on the outer wall of the inner lumen, on the outer wall of theouter lumen, and on a combination of those two cases wherein the sensorsare located at different locations on the longitudinal axis. The sensorsfurther comprise a plurality of sensors along a common plane.

FIGS. 7A-7C show examples of a prosthesis that has plurality of sensorslocated on the outer wall of the inner lumen, on the outer wall of theouter lumen, and on a combination of those two cases which furthercontain multiple sensors which are disposed axially.

FIGS. 8A-8A1 and 8B-8B1 show a side view and end view of examples of aprosthesis with a plurality of sensors located on the outer wall of theinner lumen, on the outer wall of the outer lumen, and on a combinationof those two cases which are axially separated from one another.

FIGS. 9A-9B show a prosthesis containing a number of elongated sensorson either the outer wall of the inner lumen or the outer wall of theouter lumen wherein these sensors are arrayed circumferentially aroundthe graft.

FIG. 10 shows a prosthesis containing a number of elongated sensors oneither the outer wall of the inner or the outer wall of the outer lumenor some combination thereof wherein these sensors are arrayedcircumferentially around the graft.

FIGS. 11A-11B show examples of a prosthesis with a plurality of sensorslocated on the outer wall of the inner lumen, on the outer wall of theouter lumen, where the sensors have different orientations.

FIG. 12 shows a prosthesis where sensors of different orientations maybe on either the outer wall of the inner lumen, or the outer wall of theouter lumen or some combination thereof.

FIGS. 13A-13C show examples of a prosthesis with a plurality ofhelically disposed sensors located on the outer wall of the inner lumen,on the outer wall of the outer lumen, and on a combination of those twocases, which are axially separated from each other.

FIG. 14 shows a prosthesis where a sensor which is substantiallyparallel to the longitudinal axis may be disposed on either the outerwall of the inner lumen or on the outer wall of the outer lumen.

FIGS. 15-15A show a side view and end view of a prosthesis where an openband sensor is disposed on the outer wall of the inner lumen and can beat any angle relative to the longitudinal axis.

FIGS. 16A-16A1, 16B-16B1, 16C-16C1, and 16D-16D1 show an end view and aside view of examples of a prosthesis where an undulating sensor isdisposed on either the outer wall of the inner lumen, or on the outerwall of the outer lumen. Other examples show an undulating sensordisposed on either the outer wall of the inner lumen or the outer wallof the outer lumen, which is not fully circumferential.

FIGS. 17A-17B show a prosthesis and sensor which has a collapsedconfiguration sized for delivery of the package, and an expandedconfiguration adapted to match the anatomy in which the sensor isdeployed.

FIGS. 18A-18D show side views and end views of a prosthesis wherein asensor forms a closed annular band around either the outer wall of theinner lumen or the outer wall of the outer lumen.

FIGS. 19A-19D show side views and end views of a prosthesis wherein thesensor does not form a complete loop around either the outer wall of theinner lumen or the outer wall of the outer lumen.

FIG. 20 shows a system where a tubular prosthesis is monitored by asensor and the data is then processed and transmitted to a medicalpractitioner for review.

FIGS. 21A-21B show a prosthesis where a sensor is coupled to the innerwall of the inner lumen or the outer wall of the inner lumen.

FIGS. 22A-22B show a prosthesis, such as a stent-graft, where a sensoris coupled to the outer wall of the inner lumen or the inner wall of theinner lumen.

FIG. 23 shows a prosthesis which is attached by end-to-end anastomoses.

FIG. 24 shows a prosthesis which is attached by end-to-side anastomoses.

FIG. 25 shows a prosthesis, such as a stent graft, which is used tobridge an aneurysmal sac.

FIGS. 26A-26B show a prosthesis.

FIGS. 27A-27D show a prosthesis wherein an expandable member or otherintervention is utilized to increase patency within the lumen.

FIG. 28 shows a prosthesis which is attached by end-to-side anastomosesbetween two distinct vessels, such as a fistula.

FIG. 29 shows a prosthesis which is slidably engaged over the top ofanother tubular conduit.

FIG. 30 shows characteristics of a signal representing the fluid flow.

DETAILED DESCRIPTION OF THE INVENTION

Specific embodiments of the disclosed device, delivery system, andmethod will now be described with reference to the drawings. Nothing inthis detailed description is intended to imply that any particularcomponent, feature, or step is essential to the invention.

Disclosed herein are exemplary embodiments of methods, systems anddevices which allow the medical practitioner to receive various dataparameters related to health, noninvasively, after implantation of themeasurement device within an animal or person. Without being limited toany specific use the exemplary embodiments of methods, systems anddevices disclosed herein relate to measurement of health and functioningof fluid-carrying hollow conduits within an animal or person. Exemplarydata parameters being measured by the embodiments disclosed herein maybe related to, but not necessarily limited to any of the following:occlusion of the conduit, flow velocity, flow rate, conduit wallthickening, neointimal hyperplasia, and stenosis. One of the exemplaryembodiments which will be described herein is a synthetic vascular graftwith a sensor that will provide information about blood flow through thegraft. Other exemplary embodiments will be described where a sensor isincorporated with other tubular prostheses such as stent-grafts orstents, or grafts based upon natural vessels and/or synthetic vesselsbased on stem cells.

The device will require a deployment vehicle with a hollow conduit tocarry the sensor. This can be accomplished by incorporating the sensorwith an expanded polytetrafluoroethylene (ePTFE), PTFE or polyethyleneterepthalate vascular graft or as a stand-alone implantable alsoconsisting of ePTFE, PTFE or polyethylene terepthalate. It would also bepossible to incorporate the sensor into other types of vascular graftsincluding autografts, biodegradable grafts, stent-grafts, stents orother prosthetic devices with fluid flowing through the device. In orderto prevent biofouling of the present invention; the device mayincorporate an anti-fouling coating similar to paclitaxel, ticlodipine,or other therapeutic agents or coatings known in the art.

The sensor will be used to determine the presence, and/or degree, and/orlocation of abnormal flow patterns, occlusions, flow velocity, flowrate, wall thickening, or stenosis within the hollow conduit. In oneexemplary embodiment of this invention, a tactile sensor array utilizinga piezoresistive element, such as polyvinylidene fluoride (PVDF) may beutilized as the sensor. In another exemplary embodiment of thisinvention, a cilia-like sensor array utilizing PVDF (or similar) isenvisioned. The deflection of the PVDF cilia due to blood flowtranslates into a change in voltage output provided by the sensor. Inyet another exemplary embodiment of the invention, the sensor mayincorporate biomarker sensing capability. For example, a biomarker forthromboxane A2, an inflammatory mediator present during clot formation.

The voltage change determined by the piezoresistive array may then betransmitted to a low-power application-specific integrated circuit (IC)integrated with the deployment vehicle which converts this data into aflow velocity (cm/s) or flow rate (cc/s) upon excitement by an externalreader.

An external reader may utilize radiofrequency induction to activate theIC periodically and acquire the flow data. The data would then betransmitted either directly, via an electronic medical record system, orother application to the patient's primary care physician and vascularsurgeon. In one embodiment the external reader is a handheld wand orother suitable device which can be activated either automatically or bythe user when in proximity to the device and sensor. In anotherembodiment the reader would be a stand-alone monitor which couldperiodically interrogate the IC in a user-determined manner eithercontinuously or periodically. Data may be transmitted in any number ofways including via Bluetooth protocols, via the cell phone system, vianear field communication, over the Internet, etc.

There are several challenges associated with incorporation of a sensorwith a hollow conduit. The sensor must be incorporated with the hollowconduit so that it can accurately assess various data parametersrelating to flow with little to no disturbance of the fluid flow withinthe conduit or the ability of the conduit to respond to fluid flow. Thesensor must also retain its function within the animal or person for anextended period of time, meaning it should be resistant to biofouling.It is also important that the sensor has low immunogenicity so that itcauses only minimal immune responses, and avoids causing responses whichcan result in damage to the host or damage to the device that causes thedevice to stop working.

An exemplary embodiment of the invention is illustrated in FIG. 1. Thisembodiment discloses a prosthesis for monitoring a characteristic offlow with the said prosthesis comprising a first tubular prosthesis, asecond tubular prosthesis having a lumen extending therethrough, whereinthe first tubular prosthesis is disposed over the second tubularprosthesis thereby forming a pocket therebetween; and a sensor fordetecting a characteristic of fluid flowing through the lumen of thesecond tubular prosthesis, wherein the sensor is disposed in the pocket,and wherein the sensor is preferably insulated from contact with fluidflowing through the lumen. In the exemplary embodiment displayed in thefigure, 2 represents a hollow conduit that is a tubular prosthesisdisposed outside of 3, which represents a hollow conduit that is atubular prosthesis. 1 is the lumen of 3 through which bodily fluids suchas blood would preferably flow. 8 refers to the sensor element that isdetecting a characteristic of fluid flowing through 1.

In other exemplary embodiments the aforementioned hollow conduits may beallograft vessels, xenograft vessels or tubular prostheses such asgrafts, stent-grafts or stents made from materials such as ePTFE, PTFE,polyester, polyethylene terephthalate, nitinol, biodegradable materialssuch as PLA or PGA, or another suitable flexible and/or expandablesubstrate used as a tubular prosthesis in the body. The aforementionedconduits are preferable for usage in this device because they arecommonly used in applications for vascular grafts and have wellunderstood procedures and successful outcomes associated with their usein the body. In addition, one of the two conduits in this exemplaryembodiment may also be formed from self-assembled monolayers (SAMs)based on a suitable chemistry such as silane, thiol, or phosphonate. Useof SAMs would preferably enable an easily manufactured conduit to beformed on the inner or outer region of the first conduit.

Tubular prostheses are a preferred embodiment for this device due to thefact that sensor integration with a synthetic conduit will be moredesirable than sensor integration with an allograft or xenograft fromsafety, manufacturing and clinical perspectives. An exemplary embodimentwhich incorporates a sensor with a tubular prosthesis or prostheses willpreferably create little to no increase in immunogenicity in comparisonto a simple tubular prosthesis because all of the materials in thedevice are regarded as foreign by the body's immune system. However, inthe exemplary embodiment where a sensor is incorporated with anallograft or xenograft, the immunogenicity of the embodiment may be muchgreater than a simple allograft or xenograft since the device will haveboth natural and synthetic materials and the body's immune system willnow perceive the entire system to be foreign rather than native.Furthermore, manufacturing processes of tubular prostheses are wellunderstood by those skilled in the art and can be modified more easilyfor large-scale manufacturing of the exemplary embodiment whichincorporates a sensor with tubular prostheses. Also, due to the highclinical failure rate of tubular prostheses, the need for a deviceenabling monitoring of health parameters relating to flow through aprosthesis is significantly higher than for an allograft or xenograft.

In the aforementioned embodiment (FIG. 1), the sensor would preferablybe disposed in a negative space, or pocket between the two conduits. Theinner surface of the inner conduit would be in contact with the bodilyfluid, and at least partially shield the sensor from direct contact withthe bodily fluid, while the outer conduit would preferably limit thesensor's exposure to the body's immune responses that could lead todamage to either the host or device. The configuration in this aspect ofthe invention preferably enables the sensor to assess parametersrelating to patient health including but not limited to non-laminarflow, presence or location of an occlusion, flow rate, flow velocity,pulse rate, conduit wall expansion, conduit wall thickness, or stenosiswithout significantly interfering with the ability of the hollow conduitto function at an adequate capacity. The sensor preferably will be ableto effectively detect various parameters relating to patient healthbecause energy from fluid flow through the inner conduit would betransmitted to the sensor through the wall of the conduit. Severalvariations of this arrangement are possible and selection of one or moreof these variations can depend on desired features for the particularapplication. Some of these will be discussed later.

FIGS. 21 and 22 disclose additional exemplary embodiments of theinvention. The figures disclose examples of a prosthesis for monitoringflow, said prosthesis comprising a first tubular prosthesis having alumen extending therethrough, a sensor coupled to the first tubularprosthesis, wherein the sensor is configured to sense fluid flow throughthe lumen; and a layer of material disposed over the sensor andpreferably sealingly coupled to a surface of the first tubularprosthesis thereby encapsulating the sensor such that the sensor isinsulated from contact with fluid flowing through the lumen.

FIG. 21a discloses an exemplary embodiment where a tubular prosthesis(object 4) has a sensor (object 47) coupled to the inner surface of 4,or in other words within the lumen of 4. A layer of material (object 6)is disposed over 47 and sealingly coupled to the surface of 4. Dependingon the choice of coupling method, material for 6, sensor size, and otherparameters, a pocket may be formed (object 7) between 6 and 47. FIG. 21bdiscloses another exemplary embodiment, similar to the one disclosed inFIG. 21a , except the sensing element (object 48) is coupled to theouter surface of 4 with a layer of material (object 6) sealingly coupledto the outer surface of 4. FIG. 22 discloses exemplary embodiments wherethe tubular prosthesis is a stent graft. As shown in FIG. 22a the sensorelement (object 49) is disposed between the stent (object 5) and graft(object 4), coupled with the stent-graft with an additional layer(object 6) sealingly coupled to 4. In this embodiment the sensor liesoutside of the graft lumen, 1. As with FIG. 21, a pocket (object 7) maybe formed depending on the coupling methods between 6 and 4 as well asother factors. FIG. 22b is similar to 22 a, except the sensor (object50) is coupled to the inner surface of 4 as opposed to between 4 and 6.The key difference between FIGS. 22a and 22b is that the sensor elementin 22 b is disposed within 1, the lumen of 4.

In the exemplary embodiments listed above, a sensor element ispreferably coupled to a single hollow conduit with an additional layersealingly coupled over the sensor so it preferably limits exposure ofthe sensor to bodily fluid and/or tissue. In exemplary embodiments theadditional layer may be a patch or a concentric circumferential ring ofmaterial. In another exemplary embodiment, the hollow conduit can be anallograft vessel, xenograft vessel, or a tubular prosthesis such as agraft, prosthetic vascular graft, stent-graft or stent made of ePTFE,PTFE, polyester, polyethylene terephthalate, biodegradable materialssuch as PLA or PGA, or other flexible and/or expandable substrates suchas nitinol. The additional layer of material can be made from any numberof materials that are biocompatible, flexible, and will notsignificantly degrade over the lifetime of the device. The fluid flowingthrough this device in many cases will preferably be a bodily fluid suchas blood and the device will be measuring parameters relating to flow ofblood through the conduit. It may be beneficial from both amanufacturing and sensor function standpoint to construct thisadditional layer from the same material that is being used in the hollowconduit. The sensor may see improved functioning from this because oflower impedance mismatch between the sealing layer and the conduit.Possible materials for the sealing layer include but are not limited toePTFE, PTFE, polyester, polyethylene terephthalate, nitinol, silicone,polydimethyl siloxane (PDMS), poly vinyl alcohol (PVA), parylene orother thin film polymer coatings. The additional layer may also beconstructed from self-assembled monolayers (SAMs) based upon silane,thiol, or phosphonate chemistries. SAM protective layers preferablywould produce a minimal feature over the device while being sealinglycoupled to the hollow conduit and preferably also provide the necessaryprotective barrier to limit exposure to tissue and fluids in the body.SAMs preferably would also avoid any potential issues of impedancemismatch from other capping materials or adhesives and also enableeasier manufacturing of the device. To potentially minimize thedisruption of flow through the hollow conduit, one exemplary embodimenthas the sensor coupled to the outer surface of the hollow conduit(sometimes also referred to herein as a tubular prosthesis with a lumen)with the additional layer sealingly coupled over the sensor. In casethis embodiment does not produce sufficient sensitivity, an alternativeembodiment has the sensor coupled to the inner surface of the hollowconduit with the additional layer sealingly coupled over the sensor.

In one exemplary embodiment with a sensor disposed in a pocket betweentwo hollow conduits such as the embodiment disclosed in FIG. 1, bothhollow conduits will be tubular prostheses such as a graft made of avascular graft material such as ePTFE, PTFE, polyester or polyethyleneterepthalate. This embodiment could be especially advantageous forvascular bypass procedures where a clinician needs to repair anobstructed or damaged blood vessel and create a conduit to support bloodflow from one region of the body to another. The medical practitionerpreferably would be able to surgically place the device into the body asif it were a typical vascular graft. Also, the immune response for sucha device preferably would be more easily predictable because the body'sfluids and immune system will only be exposed directly to materials thathave been rigorously tested for safety and commonly used forimplantation over multiple decades.

In another exemplary embodiment of the prosthesis disclosed in FIG. 1,one prosthesis will be made from a vascular graft material such aspolyester, ePTFE, PTFE, or Polyethylene terepthalate, or a biodegradablematerial such as PGA or PLA, while the other prosthesis will be a stent,which can be made from a flexible and/or expandable metallic alloy suchas superelastic or shape memory alloys made from nitinol, balloonexpandable materials such as stainless steel, cobalt chromium alloy orother metals. The stent may be balloon expandable or self-expanding.This embodiment is advantageous for endovascular procedures andpreferably enables the practical application of this sensor intostent-grafts. However, one potential disadvantage of this embodiment maybe that the stent prosthesis is known to be very porous and thus mayprovide minimal protection of the sensor from exposure to the body.Another alternative embodiment that could address this issue will have asensor disposed between two tubular prostheses made of a vascular graftmaterial such as ePTFE, PTFE, polyester or polyethylene terepthalate.This entire system would then be disposed within or around anothertubular prosthesis, such as a stent made from a flexible and/orexpandable substrate, such as nitinol, stainless steel or cobaltchromium alloy. This preferably would enable protection of the sensor bya less porous material than a stent, while still enabling use of thisdevice in stent-grafts. In another exemplary embodiment, the sensor isdisposed in a pocket between two hollow conduits, where the innerconduit consists of a naturally occurring vessel found in the body, andthe outer conduit can be any suitable protective vessel material,including, but not limited to PTFE, ePTFE, polyester, polyethyleneterepthalate, or a natural cellular barrier. This embodiment could beideal for venous cuff surgeries which are used to mitigate the immuneresponse to a vascular graft placement in the body. In another exemplaryembodiment of the prosthesis disclosed in FIG. 1, the inner conduitconsists of a vessel grown outside of the patient's body from stemcells, or another biological source, and the outer conduit can be anysuitable protective vessel material, including but not limited to PTFE,ePTFE, polyester, polyethylene terepthalate or a natural cellularbarrier.

In the prostheses disclosed in FIGS. 1, 22, and 23, the nature of thecoupling between two conduits, or a conduit and an additional layer canaffect a number of aspects of the device, including signal propagation,signal detection, manufacturing, and device lifetime. Several exemplaryembodiments of the nature of the coupling would be desirable and all ofthese mentioned herein may be applied or combined with any of theexemplary embodiments mentioned herein. In one exemplary embodiment theobjects of interest are integrally coupled. For the embodiment in FIG.1, these objects of interest are 2 and 3, for the embodiments in FIGS.21 and 22, the objects of interest are 6 and 4. Integral coupling mayminimize potential issues related to interference with signaltransduction, and preferably also improve the longevity of the devicesince no adhesives or sutures are required to maintain the connectionbetween both conduits. One approach for achieving integral coupling isto sinter the objects of interest together. In another exemplaryembodiment objects of interest are fixedly coupled to one another eitherthrough a bonding agent, adhesive, or other chemical treatment. Thisapproach may offer benefits for manufacturing while also providingsufficient robustness for long-term stability in the body. In yetanother exemplary embodiment, the objects of interest may be sutured orstapled together. The benefits of suturing and stapling are that itallows for more easy modification and customization of integrationbetween two conduits or a conduit and an additional layer. This could beespecially important during a surgery or other clinical interaction. Inaddition, sutures and staples are well known to those skilled in the artthat are biocompatible, nonimmunogenic, and will robustly survive forlong periods of time as an in vivo implant. In another exemplaryembodiment both hollow conduits are entirely discrete. This may beadvantageous in cases where the dimension or materials chosen for theconduits enable enough mechanical or physical adhesion to preclude anyneed for adhesive, integral, or other forms of coupling. In analternative embodiment, the two hollow conduits may be two tubularprostheses that are integral with one another and in which a pocket hasbeen formed to hold the sensor.

FIG. 1 discloses a prosthesis wherein the first tubular prosthesis has afirst length and the second tubular prosthesis has a second lengthsubstantially the same as the first length. FIG. 2 discloses aprosthesis similar to the one disclosed in FIG. 1 except in FIG. 2 thefirst tubular prosthesis (object 2) has a first length and the secondtubular prosthesis (object 3) has a second length shorter than the firstlength. The sensor (object 9) is disposed between 2 and 3 just as inFIG. 1. FIG. 3 discloses a prosthesis similar to the one disclosed inFIG. 1, except in FIG. 3, the first tubular prosthesis (object 2) has afirst length and the second tubular prosthesis has a second length(object 3) longer than the first length. The sensor (object 10) isdisposed between 2 and 3 just as in FIG. 1.

The exemplary embodiments disclosed in FIGS. 1,2 and 3 demonstrate thatthe length of each conduit with respect to the other can be a key aspectto consider in device design. Any of the features of disclosed inexemplary embodiments of this aspect of the invention may be combinedwith or substituted for any of the features in other exemplaryembodiments described herein. The exemplary embodiment of FIG. 1 wouldenable simpler and more efficient manufacturing of the device and alsoprovide a more complete barrier between the sensor and the surroundingtissue, potentially making the device less immunogenic. The exemplaryembodiment disclosed in FIG. 2 reduces the cost of materials for thedevice because less materials are used per device in comparison to theembodiment where both conduits have identical length. The exemplaryembodiment disclosed in FIG. 3 may be advantageous because of therelatively lower cost of materials in this embodiment, and also becausethe inner conduit in this embodiment remains undisturbed.

In all of the aforementioned exemplary embodiments, the sensorpreferably fulfills several requirements in order to function accuratelyand to be able to be incorporated successfully with a hollow conduitsuch as a tubular prosthesis. It is preferably flexible or conformableto a tubular structure, able to respond to acoustic and mechanicalsignals transmitted through a wall, and also is able to transduce theacoustic/mechanical signals it detects into electrical signals so thatthe sensor output can be interpreted by an integrated circuit ortransmitter. In any embodiment of this device, because it will be along-term implant in the body and thus, be unable to access a powersource easily unless one is implanted into the body, it is desirable forthe sensor to be low-power, and ideally, completely passive. Mostimportantly, the sensor must be able to withstand the conditions in thebody over time with minimal drift in the final output and also not be adanger to the person or animal. Because of the specific need fortransduction of acoustic/mechanical signals into electrical signals, apiezoelectric sensor would be a likely choice for the sensing element.Use of a piezoelectric sensor also enables the detection and assessmentof Doppler signals, which means the piezoelectric element also functionsas a Doppler sensor. A polyvinylidine fluoride (PVDF) thin film sensormeets all of the above requirements and is therefore a preferredembodiment of the sensor element in the device. In particular, PVDF filmsensors are known to respond to mechanical and acoustic signals withvery large electrical signals, even when they are completely passive.This means a PVDF sensor does not draw or require any power at all tofunction. These capabilities are due to the piezoelectric properties ofPVDF which result from the molecular and electron structure that resultsfrom well-established manufacturing methods. These properties enable thesensor to transduce mechanical and acoustic signals into electricalsignals without the need for any external power source. PVDF isavailable in films, and methods are well known to those skilled in theart for fabricating various designs of PVDF film sensors. PVDF filmsensor response is also influenced by changes in temperature. Thermalchanges can be used to assess a variety of health parameters in a hollowconduit including but not limited to non-laminar flow, occlusion, flowrate, flow velocity, wall thickening, or stenosis. PVDF film sensorsalso operate across a very wide band of frequency ranges, meaning thatvery low frequency and high frequency signals can be detected with thesesensors. Another feature of PVDF film sensors that could beneficial tothe device is their ability to act as a source for energy harvestingfrom the body. Since PVDF films are able to translate mechanical energyinto electrical energy in a passive manner, energy harvesting systemswhich are known to those skilled in the art, may be constructed to helpoffset the power requirements of other components in the device.

A PVDF film sensor deployed with a hollow conduit can be used to detecta variety of signals relating to the subject's health. In the exemplaryembodiments described above where a PVDF film sensor is incorporatedwith one or more hollow conduits such as a xenograft, allograft, ortubular prosthesis such as a graft, stent, or stent-graft, the sensorcan detect a number of parameters which ultimately relate to bothsubject health and fluid flow. The PVDF sensor can detect mechanicalsignals exerted by fluid flowing through the conduit such as strain,stress, or pressure. The PVDF sensor will also respond to acousticsignals generated by fluid flowing through the conduit. As mentionedearlier, the PVDF sensor will also be responsive to thermal changes.Taken individually or together these parameters enable the detection ofvarious parameters that are critical to subject health including but notlimited to flow velocity (cm/s), flow rate (volumetric), stenosis, wallthickness, flow turbulence, non-laminar flow, occlusion, level ofocclusion or occlusion location. For an exemplary embodiment where thehollow conduit is a tubular prosthesis that is utilized for blood flow,the ability to detect flow velocity, flow rate, level of occlusionand/or occlusion location are particularly valuable. Experiments havebeen conducted with this embodiment to determine whether it could beused to assess these and other health parameters relating to blood flowthrough a vascular graft. The experiments suggest that such anembodiment can successfully determine occlusion level, flow rate, flowvelocity and location of an occlusion utilizing the PVDF sensor'sability to detect pressure and acoustic signals. The experiment andresults are described briefly below.

Experimental Results

Experiments were conducted with a PVDF film sensor incorporated with anePTFE vascular graft with an additional layer sealingly coupled over thesensor. Biological fluid flow was simulated by attaching the vasculargraft to a Harvard Apparatus large animal heart pump and pumping waterand blood mimicking fluid (ATS Medical) through the system. The systemwas implanted into ballistics gel to mimic an in vivo tissueenvironment. Constrictions were applied upstream and downstream of thePVDF sensor to determine its ability to respond to occlusions in theflow. Stroke volume, heart rate, and diastole/systole ratio were variedon the pump to determine the device's ability to detect variousparameters relating to flow and the graft. Through these experiments, itwas determined that the device is able to detect changes in flow rate,flow velocity, the level of occlusion, the location of an occlusion, andturbulence of flow.

Several possible sensor configurations can exist in the embodimentsdescribed above where a PVDF sensor is incorporated with one or morehollow conduits and the exemplary embodiments of sensor configurationsdescribed herein may be incorporated with one or more hollow conduits inany of the exemplary embodiments mentioned herein. As mentioned earlier,these hollow conduits may be allograft vessels, xenograft vessels ortubular prostheses such as grafts or stents made from materials such asePTFE, PTFE, polyester, polyethylene terephthalate, biodegradeablematerials, nitinol, or another suitable flexible and/or expandablesubstrate used as a tubular prosthetic in the body. A plurality ofindividual sensor embodiments or some combination of the sensorembodiments mentioned herein may be used in the device. Differentconfigurations of a PVDF sensor will result in different sensorresponses due to PVDF film orientation, pattern and shape. This isbecause piezoelectric PVDF films are axially oriented and provide adifferential electrical response in each axis. For the purposes of thisdiscussion the “x-axis” will be used to refer to the most sensitive axisof the PVDF film sensor.

PVDF film sensors may be utilized as sensor elements in some or all ofthe exemplary embodiments described herein. In one exemplary embodimentthe x-axis of the sensor will be oriented parallel to the longitudinalaxis of the hollow conduit(s). When oriented in this fashion, the sensorwill be more sensitive to mechanical and acoustic waves propagatinglengthwise down the longitudinal axis of the hollow conduit. In anotherexemplary embodiment the x-axis of the PVDF sensor will be perpendicularto the longitudinal axis of the hollow conduit(s) and thus be disposedcircumferentially around either hollow conduit. This enables the sensorto be more sensitive to mechanical and acoustic signals directedperpendicularly from the circumferential axis of the hollow conduit.Through experimentation, this has been determined to be the preferredorientation of the PVDF film for sensitivity to fluid flow through agraft. This is due to the fact that circumferentially oriented strainsand acoustic signals are more correlated to fluid flow rates andcharacteristics through the graft than longitudinally oriented signals.Longitudinally oriented signals appear to be more a function of heartrate than fluid flow properties. Another exemplary embodiment whichwould allow simultaneous measurement of both longitudinally andcircumferentially oriented signals is a sensor which is oriented at anangle or transverse to the longitudinal axis of the hollow conduit(s).The sensor could be interrogated in such a way that flow, pulse, andother data signals can be collected during data analysis from a singlesensor. In another exemplary embodiment, a plurality of sensors aredisposed circumferentially around one or more hollow conduits with thex-axis of each sensor aligned identically with relation to thelongitudinal axis of the hollow conduit. In this embodiment, comparisonof sensor responses at different locations in the hollow conduit couldbe useful for assessing changes in various data parameters of interestthat have been mentioned herein. This embodiment in particular is usefulfor assessing changes in various data parameters as a function oflocation since the sensor would be oriented and disposed in a similarfashion with the conduit at various locations. In another exemplaryembodiment a plurality of sensors wherein each sensor is disposeddifferentially from the other with respect to their orientation with thelongitudinal axis of the hollow conduit(s). The benefit of thisembodiment is that it will be possible to assess various distinct dataparameters from with a dedicated sensor for each parameter. For example,one sensor may be disposed circumferentially around a hollow conduitwith the x-axis of the PVDF film sensor being perpendicular to thelongitudinal axis, while a second sensor is disposed in such a mannerthat the x-axis of the PVDF film is parallel to the longitudinal axis.This would enable detection of both longitudinally and circumferentiallyoriented signals from the hollow conduit with a dedicated sensor foreach type of signal. In another exemplary embodiment, a plurality ofsensors exists wherein each sensor is disposed differentially from theother with respect to their orientation with the longitudinal axis ofthe hollow conduit(s) and each sensor is helically incorporated with thehollow conduit(s) such that a length of the conduit(s) has multiplehelical sensors. This embodiment would enable detection of multipleparameters as well as assessment of changes of each parameter withrespect to location over a length of the conduit. Another exemplaryembodiment with a PVDF sensor disposed between two hollow conduits wouldhave the PVDF sensor forming a serpentine pattern around the innerconduit. This would essentially orient the film in both the longitudinaland circumferential axes at various points around the serpentinepattern, and thus both capture signal in the longitudinal axis as wellas the circumferential while still allowing expansion of the conduit,thus not interfering with its functionality. Finally, in anotherexemplary embodiment the PVDF sensor forms a candy-stripe pattern aroundthe inner conduit. This last pattern would allow for signal to beobtained from both the longitudinal and circumferential axes. While somesignal in each would be lost, it would also allow for any time varyingparameters associated with flow to be obtained. Such parameters mayinclude the transit time of a pulse between the two candy stripes or thephase shift of a pulse between the two candy stripes. Using a pluralityof any of the aforementioned sensors enables the interrogation ofmultiple parameters relating to flow at once. In addition, multiplesensors can be used to perform transit time measurements in alternativeembodiments.

Another key aspect to consider for a PVDF sensor incorporated with anyof the exemplary embodiments described herein is shape and coverage ofthe sensor on the hollow conduit. This can affect function andsensitivity of the device. In one exemplary embodiment the PVDF sensorforms a complete loop around the circumference of the outer or innerwall of a hollow conduit. This maximizes the ability of the sensor torespond to circumferentially oriented signals. However, this embodimentalso has the potential to constrict expansion of the inner conduit,which may adversely affect the conduit and its ability to sustainhealthy, normal fluid flow. Another exemplary embodiment that canaddress this issue consists of a PVDF sensor which covers<360 degrees ofthe circumference of the outer or inner wall of a hollow conduit. Whilepart of the circumferentially oriented signals may be lost or the signalmay be reduced in strength, in this embodiment the conduit can moreeasily expand in response to fluid flow. In another exemplaryembodiment, the PVDF film sensor will cover about 170-190 degrees of thecircumference of one or more hollow conduits with the x-axis of thesensor being oriented circumferentially with respect to the conduit. Theadvantage of this embodiment is that when a PVDF film sensor coversroughly half the circumference of a hollow conduit, it maximizes thestretch that the sensor would undergo as a result of circumferentialsignals for sensor configurations where the film does not cover the fullcircumference of a conduit.

FIG. 4 discloses an exemplary embodiment of the prosthesis disclosed inFIG. 1 wherein the sensor is disposed circumferentially around the firstand/or second tubular prosthesis. Object 11 is a sensor which is coupledaround the first tubular prosthesis (object 2), while object 12 is asensor coupled around the second tubular prosthesis (object 3). In thecase of the PVDF film sensor mentioned herein, the x-axis of the sensorwould be oriented circumferentially to enhance sensitivity tocircumferentially oriented signals resultant from flow. Examples ofthese signals are pressure, wall expansion, etc. Other exemplaryembodiments relating to FIG. 4 may include one or both sensors invarious configurations and combinations with other exemplary embodimentsdisclosed herein. To maximize sensitivity to circumferentially orientedsignals, the sensor in FIG. 4 can be oriented orthogonally to thelongitudinal axis of 2 or 3. If sensitivity to both circumferentiallyoriented and longitudinally oriented signals is desired the sensor inFIG. 4 would be circumferentially disposed but, not orthogonally to thelongitudinal axis of 2 or 3.

FIG. 5 discloses exemplary embodiments of FIG. 1 wherein the sensorcomprises a plurality of sensors disposed circumferentially around thefirst and/or the second tubular prosthesis. In FIG. 5a twocircumferentially oriented sensing elements (objects 13) are disposedaround the second prosthesis (object 3) and within the first prosthesis(object 2). In FIG. 5b , two circumferentially oriented sensing elements(objects 14) are disposed around the first prosthesis (object 2). InFIG. 5c , two circumferentially oriented sensing elements are depictedwith one sensor (object 14) being disposed around the first prosthesis(object 2) and the second sensor (object 13) being disposed around thesecond prosthesis (object 3) and within the first prosthesis (object 2).The benefits of using a plurality of sensors is manifold. Redundancy isa desirable characteristic for any sensing system that will be used inthe body. In addition, when using multiple sensors, transit timemeasurements may be performed to assess characteristics relating toflow. A plurality of sensors preferably also enables measurement ofvarious parameters at various locations along the prosthesis. Variouscombinations of the embodiments disclosed in FIGS. 5a, 5b, and 5c arepossible both with each other and with other exemplary embodimentsdisclosed herein.

FIG. 6 discloses exemplary embodiments of the prosthesis of FIG. 1wherein the sensor comprises a plurality of discrete sensors disposedcircumferentially along the first and/or the second tubular prosthesis.In FIG. 6a two rings of multiple discrete sensors (objects 15) aredisposed circumferentially around the second prosthesis (object 3) andwithin the first prosthesis (object 2). In FIG. 6b two rings of multiplediscrete sensors (objects 16) are disposed circumferentially around thefirst tubular prosthesis (object 2). In FIG. 6c two rings of multiplediscrete sensors are depicted with one ring of multiple discrete sensors(objects 16) disposed circumferentially around the first tubularprosthesis (object 2) and a second ring of multiple discrete sensors(objects 15) disposed circumferentially around the second tubularprosthesis (object 3) and within the first tubular prosthesis (object2). The exemplary embodiments disclosed in FIG. 6 may be used incombination with any of the exemplary embodiments described herein. Thebenefit of using multiple discrete sensors in a circumferentiallyoriented ring is that measurement of circumferentially oriented signalsrelated to flow is still possible in these exemplary embodiments, butnow the variation and changes in signal along the circumferential axiscan be measured. This could be desirable in vascular applications interms of assessing non-uniformity of flow or development ofabnormalities in the lumen (object 1) of the tubular prosthesis sinceblockages can form at one point location along a circumference, ratherthan uniformly around an entire circumference of the prosthesis.

FIG. 7 discloses exemplary embodiments of FIG. 1 wherein the sensorcomprises a plurality of discrete sensors disposed axially along thefirst and/or the second tubular prosthesis. In FIG. 7a a plurality ofdiscrete sensors (objects 17) are disposed axially along the outersurface of the second prosthesis (object 3) and within the firstprosthesis (object 2). In FIG. 7b a plurality of discrete sensors(objects 18) are disposed axially along the outer surface of the firstprosthesis (object 2). In FIG. 7c one plurality of discrete sensors(objects 18) are disposed axially along the outer surface of the firstprosthesis (object 2) and another plurality of discrete sensors (objects17) are disposed axially along the outer surface of the secondprosthesis (object 3) and within the first prosthesis (object 2). Theexemplary embodiments disclosed in FIG. 7 may be used in combinationwith any of the other exemplary embodiments described herein. In theembodiments described in FIG. 7, the plurality of axially disposedsensors may be disposed parallel to the longitudinal axis of theprosthesis or they may not be. If they are disposed substantiallyparallel to the longitudinal axis of the prosthesis, the sensorspreferably will be able to respond most sensitively to longitudinallydirected signals. If they are disposed in such a manner that they arenot substantially parallel to the longitudinal axis of the graft, theypreferably will be able to respond sensitively to both longitudinal andcircumferentially directed signals. The embodiments described in FIG. 7are desirable because they may enable assessment of parameters relatedto the flow at discrete locations along the length of a tubularprosthesis. This could be helpful in identifying vulnerable locationsalong the length of the prosthesis and guide intervention decisions forclinicians.

FIG. 8 discloses exemplary embodiments of the prosthesis disclosed inFIG. 1, wherein the sensor comprises first and second annular bandscircumferentially disposed around the first and/or the second tubularprosthesis, and wherein the first annular band is axially separated fromthe second annular band. In FIG. 8a two annular band sensors (objects19) are circumferentially disposed around the first prosthesis (object2) and axially separated from one another. In FIG. 8b two annular bandsensors (objects 19) are circumferentially disposed around the secondprosthesis (object 3) and within the first prosthesis (object 2) andaxially separated from one another. In another exemplary embodimenteither or both of the annular band sensors form a closed loop around oneof the prosthesis (either 2 or 3). The exemplary embodiments disclosedin FIG. 8 may be used in combination with any of the other exemplaryembodiments described herein. The embodiments described by FIG. 8 aredesirable since multiple sensor elements may allow for simultaneousmeasurement of different parameters. This preferably allows for transittime measurements as well as measurement of various locations along thelength of a tubular prosthesis. In particular, two sensors may be verydesirable because they will likely have a lower power and processingfootprint than other multi-sensor embodiments while preferably stilloffering much of the same functionality specifically for transit timemeasurements.

FIGS. 9 and 10 disclose exemplary embodiments of the prosthesisdisclosed in FIG. 1, wherein the sensor comprises a plurality ofelongated sensors, the plurality of elongated sensors axially orientedalong the first and/or the second tubular prosthesis. In FIG. 9a aplurality of elongated sensors axially oriented and of differentdimensions (objects 21) are disposed on the outside of the firstprosthesis (object 2). In FIG. 9b a plurality of elongated sensorsaxially oriented and of different dimensions (objects 22) are disposedon the outside of the second prosthesis (object 3) and within the firstprosthesis (object 2). In FIG. 9c one plurality of elongated sensorsaxially oriented and of different dimension (objects 21) are disposed onthe outside of the first prosthesis (object 2) and a single, axiallyoriented elongated sensor (object 22) is disposed on the outside of thesecond prosthesis (object 3) and within the first prosthesis (object 2).The exemplary embodiments disclosed in FIGS. 9 and 10 may be used incombination with any of the other exemplary embodiments describedherein. The embodiments described by FIGS. 9 and 10 are desirablebecause they preferably allow multiple signals that are associated withthe longitudinal stretching of the graft to be interrogatedsimultaneously at different discrete lengths along the graft. Theanalysis of signal propagation along different lengths of sensor atdifferent locations would preferably allow for a more complete analysisof fluid flow through the prosthesis. Further, if the sensors arelocated longitudinally along the graft at different locations and atdifferent angles to one another, this also preferably allows theprocurement of different components of the base signal.

FIGS. 11 and 12 disclose exemplary embodiments of the prosthesis in FIG.1 wherein the sensor comprises two sensors wherein the first sensor isconfigured to capture a first characteristic of the fluid flow in thelumen, and wherein the second sensor is configured to capture a secondcharacteristic of the fluid flow in the lumen and wherein the firstsensor is disposed in a first orientation relative to the first or thesecond tubular prosthesis, and wherein the second sensor is disposed ina second orientation relative to the first or the second tubularprosthesis, and wherein the first orientation is different than thesecond orientation. In FIG. 11a a first sensor (object 23) is orientedorthogonally to the longitudinal axis of the prosthesis while a secondsensor (object 24) is oriented parallel to the longitudinal axis of theprosthesis. Both 23 and 24 are disposed outside of the second prosthesis(object 3) and within the first prosthesis (object 2). In FIG. 11b afirst sensor (object 25) is oriented orthogonally to the longitudinalaxis of the prosthesis while a second sensor (object 26) is orientedparallel to the longitudinal axis of the prosthesis. Both 25 and 26 aredisposed outside of the first prosthesis (object 2). In FIG. 12 a firstsensor (object 27) is oriented orthogonally to the longitudinal axis ofthe prosthesis and disposed outside of the first prosthesis (object 2).A second sensor is oriented parallel to the longitudinal axis of theprosthesis and disposed outside of the second prosthesis (object 3) andwithin the first prosthesis (object 2). The exemplary embodimentsdisclosed in FIGS. 11 and 12 may be used in combination with any of theother exemplary embodiments described herein. The embodiments describedby FIG. 11 are desirable because they preferably allow for nearly purecomponents of both the stretching of the prosthesis longitudinally andthe outward “bulging” of the prosthesis to be measured simultaneously.By orienting the sensors in this fashion, it will preferably not requiresignificant signal de-convolution between the “bulging” aspect of fluidflow through the prosthesis and the longitudinal stretching of theprosthesis. As an added benefit, orienting the two sensors on the samelumen (object 2 or 3) may yield less noisy data as compared to sensorsthat are on two different lumens (2 and 3). The embodiments described byFIG. 12 are desirable because they preferably allow for nearly purecomponents of both the stretching of the prosthesis longitudinally andthe outward “bulging” of the prosthesis to be measured simultaneously.As an added benefit, measuring in two planes (one or more sensors onobject 2 and one or more sensors on object 3) may preferentially beimmune to any localized stiffening effects that are caused by having twosensors in close proximity on the same plane (two sensors on object 2 or3).

FIG. 13 discloses an exemplary embodiment of the prosthesis from FIG. 1wherein the sensor comprises a plurality of sensors wherein theplurality of sensors are helically disposed around the first or thesecond tubular prosthesis. In FIG. 13a a first sensor (object 29) ishelically disposed over a length of the prosthesis, disposed over thesecond prosthesis (object 3) and within the first prosthesis (object 2).A second sensor (object 30) is helically disposed over a length of theprosthesis, does not intersect with 29, is disposed over the secondprosthesis (object 3) and within the first prosthesis (object 2). InFIG. 13b a first sensor (object 31) is helically disposed over a lengthof the prosthesis and disposed over the first prosthesis (object 2). Asecond sensor (object 32) is helically disposed over a length of theprosthesis, does not intersect with 31 and is disposed over the firstprosthesis (object 2). In FIG. 13c a first sensor (object 33) ishelically disposed over a length of the prosthesis and is disposed overthe first prosthesis (object 2). A second sensor (object 34) ishelically disposed over a length of the prosthesis, does not intersectwith 33, is disposed over the second prosthesis (object 3) and withinthe first prosthesis (object 2). The exemplary embodiments disclosed inFIG. 13 may be used in combination with any of the other exemplaryembodiments described herein. The embodiments described by FIG. 13 aredesirable because they can preferably capture multiple components of thesignal of interest with the same sensor (eg stretch and bulging) whilenot constraining the bulging as much as a closed annular band nor whilenot only sensing the stretching component like a sensor parallel to thelongitudinal axis would. As an added benefit, because there are twosensors (eg object 29 and 30) that follow one another around the lumenbut are spatially different, they are preferably also able to measureany travel time dependent signal.

FIG. 14 discloses an exemplary embodiment of the prosthesis disclosed inFIG. 1 wherein the first or the second tubular prosthesis has alongitudinal axis, and wherein the sensor is disposed substantiallyparallel to the longitudinal axis. The sensor element (object 35) isdisposed parallel to the longitudinal axis of the prosthesis, disposedon the outside of the second prosthesis (object 3) and within the firstprosthesis (object 2). The exemplary embodiments disclosed in FIG. 13may be used in combination with any of the other exemplary embodimentsdescribed herein. The embodiments described by FIG. 14 are desirablebecause this sensor arrangement preferably maximizes the stretchingcomponent of the signal relative to the “bulging” mechanical aspect ofthe fluid flow through the prosthesis. As an added benefit, given thesmall total volume of pvdf sensing material present in this sensorarrangement (eg object 35) it preferably has lower power requirementsrelative to other sensor arrangements.

FIG. 15 discloses an exemplary embodiment of the prosthesis disclosed inFIG. 1 wherein the first or the second tubular prosthesis has alongitudinal axis, and wherein the sensor is disposed transverse to thelongitudinal axis. The sensor element (object 36) is disposed transversein an open structure around 3 and within 2. The exemplary embodimentsdisclosed in FIG. 15 may be used in combination with any of the otherexemplary embodiments described herein. The embodiments described byFIG. 15 are desirable because this sensor arrangement preferably allowsfor the prosthesis (or individual lumen) to expand fully without beingconstrained (like a closed annular band would do) while at the same timeobtaining a good signal in the “bulging” direction. As an added benefit,this orientation preferably will make use of one or more non-closed loopbands at various angles to obtain better resolution for specific signalsof interest (eg signals causing the graft to “bulge” or it to stretchlongitudinally.

FIG. 16 discloses an exemplary embodiment of the prosthesis disclosed inFIG. 1 wherein the sensor comprises a plurality of undulating elongatedelements disposed over the first and/or the second tubular prosthesis.In FIG. 16a the sensor element (object 37) is an undulating elongatedelement that forms a complete ring around the circumference of theprosthesis and is disposed around 2. In FIG. 16b the sensor element(object 38) is an undulating elongated element that forms a completering around the circumference of the prosthesis and is disposed around 3and within 2. In FIG. 16c , the sensor element (object 39) is anundulating elongated element that is disposed partially around 2. InFIG. 16d , the sensor element (object 40) is an undulating, elongatedelement that is disposed partially around 3 and is disposed entirelywithin 2. The embodiments described by FIG. 16 are desirable becausethis sensor arrangement preferably allows for the prosthesis (orindividual lumen) to expand fully without being constrained (like aclosed annular band would do) while at the same time obtaining anexcellent signal in the stretching direction and a good signal in the“bulging” direction, especially at the harsh angle points on objects37-40.

FIG. 17 discloses an exemplary embodiment of the prostheses disclosed inFIG. 16 wherein the sensor has a collapsed configuration sized fordelivery of the sensor and an expanded configuration adapted tosubstantially match an anatomy in which the sensor is deployed, andwherein in the expanded configuration the sensor forms a closed annularband. In FIG. 17a the sensor (object 42) is collapsed and disposed overa collapsed stent (object 5) for delivery into a lumen (object 1) of aconduit (41). In FIG. 17b , 42 is in an expanded configuration thatmatches 1 and 41 due to the expansion of 5, and also forms a closedannular band disposed around 5. The exemplary embodiments disclosed inFIG. 17 may be used in combination with any of the other exemplaryembodiments described herein. The embodiments described by FIG. 17 aredesirable because this sensor arrangement preferably allows for theprosthesis (or lumen) to expand fully (from a starting point from whichit is collapsed) while at the same time conforming to both the collapsedand expanded shapes. In addition, the sensor (object 42) while at thesame time obtaining an excellent signal in the “bulging” direction.

FIG. 18 discloses an exemplary embodiment of the prosthesis disclosed inFIG. 1 wherein the sensor is disposed circumferentially around the firstor the second tubular prosthesis to form a closed annular bandtherearound. In FIGS. 18a and b the sensor element (object 43) isdisposed around 3 and within 2 in a closed loop structure normal to thelongitudinal axis of the prosthesis. In FIGS. 18c and d the sensorelement (object 44) is disposed around 2 in a closed loop structurenormal to the longitudinal axis of the prosthesis. The exemplaryembodiments disclosed in FIG. 18 may be used in combination with any ofthe other exemplary embodiments described herein. The embodimentsdescribed by FIG. 18 are desirable because this sensor arrangementpreferably allows for the prosthesis to get a very large signal in the“bulging” direction. This closed loop sensor (object 43) preferably willgive the strongest signal in this “bulging” direction over any othersensor trying to obtain only a signal in this direction.

FIG. 19 discloses an exemplary embodiment of the prosthesis disclosed inFIG. 1 wherein the sensor is partially disposed circumferentially aroundthe first or the second tubular prosthesis to form an open annular bandtherearound. In FIGS. 19a and b the sensor element (45) is disposedaround 3 and within 2 in an open annular band normal to the longitudinalaxis. In FIGS. 19c and d the sensor element (46) is disposed around 2 inan open annular band normal to the longitudinal axis. The embodimentsdescribed by FIG. 19 are desirable because this sensor arrangementpreferably allows for the prosthesis (or individual lumen) to expandfully without being constrained (like a closed annular band would do)while at the same time obtaining a good signal in the “bulging”direction. As an added benefit, if the sensor is oriented normal to thelongitudinal axis, it will preferably give a high quality signal in the“bulging” direction while not sacrificing significant signal intensity.

Protection of the sensor element and any components related to dataprocessing and transmission can be desirable in certain circumstances,for example 1) a bodily response to the sensor could harm the animal;and 2) a bodily response could affect the basic functioning of thedevice. Therefore, it is preferred that the sensor and any componentsrelated to data processing and transmission be protected as much aspossible from exposure to the body's immune response. To this end, anyof the embodiments mentioned herein may benefit from optional additionalprotective layers being attached to the sensor and the dataprocessing/transmission components. Given the various configurationsthat are possible for the device, a flexible or conformable protectiveis preferred to encapsulate these components. Possible materials forthis include, but are not limited to silicone, polydimethylsiloxane,polyvinylalcohol, parylene, polyester, PTFE, ePTFE, polyethyleneterepthalate, or other suitable polymer, metal, and/or metal oxide thinfilm coatings.

As described herein, there is a significant need for monitoring tubularprostheses that are used to carry bodily fluids in a subject such as ahuman patient or a veterinary patient. For example, for patients withblocked blood flow in their peripheral arteries, synthetic vasculargrafts are frequently used to bypass these blockages. These implantablegrafts are intended to last in patients for up to five years, howeverthere is a very high rate of failure of these devices within the firstyear of implantation. Typically, when a graft fails, it becomes blockedand eventually stops functioning as a blood carrying entity. When agraft reaches complete blockage it is unsalvageable and must bereplaced, or even worse, the patient must go through an amputation ofthe part of the body to which the graft was responsible for supplyingblood. Interestingly enough, grafts can be salvaged if they are notcompletely blocked. In fact, even a graft that is 95% blocked can besalvaged using a reopening procedure such as an angioplasty. Afterreopening, the vast majority of vascular grafts are able to survive fortheir intended duration in the patient. Since the vast majority of theseblockages typically form gradually over time (non-acutely), it would bepossible to entirely avoid these catastrophic and costly outcomes if asystem was developed such that the health of the graft could bemonitored regularly by a clinician. Existing approaches for solving thisproblem have a number of challenges. Currently, patients are tested 1-2times per year with duplex ultrasound, a dedicated imaging machine thatcan only be used in hospitals. Furthermore, duplex ultrasound requires ahighly trained technician and/or clinician to interpret the health ofthe graft. Because duplex ultrasound is the only technology available toclinicians today, testing can only occur in hospitals, requires aseparately scheduled appointment, is very costly, and produces resultsthat are very difficult to interpret. The gold-standard metric forassessing graft health today is measurement of peak flow velocity of theblood flow through a graft. This is then correlated to occlusionpercentages to make a determination of what course of action to takewith a patient. While this test is accurate when carried out by skilledclinicians, unfortunately, it is carried out too infrequently. Blockagesoften form in a matter of weeks, so a frequency of testing once everysix months can be inadequate. Therefore, it would be beneficial todevelop a system whereby graft health can be assessed at regularintervals from a convenient location such as a patient's home.Preferably, this system would enable remote assessment and monitoring ofthe patient's graft health such that a sensor disposed with the graft inthe patient would be able to eventually transmit data directly to aclinician, electronic medical record, hospital, or other care provider.This would allow clinicians to interpret this data and then decidewhether a further diagnostic study or other intervention such as anangioplasty would be needed.

In another aspect of the invention, a system for monitoring fluid flowthrough one or more hollow conduits such as allograft vessels, xenograftvessels or tubular prostheses such as grafts, stent-grafts or stentsmade from materials such as ePTFE, PTFE, polyester, polyethyleneterephthalate, nitinol, cobalt chromium alloy, stainless steel,bioabsorable polymers such as PGA, PLA, etc., or another suitableflexible and/or expandable substrate used as a tubular prosthetic in thebody is disclosed. This aspect of the invention or any exemplaryembodiments of this aspect of the invention may include one or severalof the exemplary embodiments described herein relating to any otherfeatures of the embodiments disclosed herein and may comprise aprosthetic with a lumen extending therethrough with the lumen configuredfor fluid flow therethrough and a sensor operatively coupled with theprosthesis and configured such that it can sense fluid flow and outputdata related to patient health, fluid flow, flow rate, flow velocity,wall thickness, stenosis, non-laminar flow, turbulent flow, occlusion,occlusion percentage, or occlusion location. In an exemplary embodiment,the system may also incorporate a wireless transmitter such that datacan be transmitted from the sensor to another location. This locationcould be a remote location, or any location that is locatedintracorporeally or extracorporeally. In another exemplary embodiment adisplay device is operative coupled with the sensor and is configured todisplay the output data. In this exemplary embodiment, the displaydevice may be operatively coupled remotely or directly with the sensor.For example, if sensor output is transmitted to one or more externaldevices and eventually to a clinician's mobile device or computer, thedisplay of the mobile device would be considered to be operativelycoupled with the sensor. A number of display devices are possible forthis including mobile phones, tablets, personal computers, televisions,instrument displays, watches, optical head-mounted displays, wearableelectronics, augmented reality devices such as contact lenses, glassesor otherwise. In another exemplary embodiment a processor is operativelycoupled with the sensor and configured to process the output data. Aswith the operatively coupled display in the prior exemplary embodiment,the processor may be operatively coupled remotely or directly to thesensor. For example, if sensor output was transmitted to one or moreexternal devices and eventually to a processor which is configured toprocess the output data, the processor would be operatively coupled withthe sensor. Several processors are known to those skilled in the art andan appropriate processor may be selected from the known art for any ofthe embodiments disclosed herein. In another exemplary embodiment thesystem further comprises an operatively coupled power source forproviding power to the system. As mentioned earlier, operative couplingmay be direct or remote. For example the power source could be a batterywhich is either implanted in the patient or resides outside of the body.Another example of a power source is an RF source which throughinductive coupling is able to supply power to the implanted componentsof the system. The benefit of an RF inductively coupled power supply isthat it eliminates the need for an implantable or otherwise directlyconnected battery. In another exemplary embodiment, the system comprisesa low power sensor which is essentially passive and does not requirepower supplied thereto to sense fluid flow. In another exemplaryembodiment the system comprises a lower power sensor and transmitterwhich are both essentially passive and do not require power suppliedthereto to sense fluid flow and output data related to fluid flow. Thebenefit of such a sensor and/or transmitter is that it minimizes thepower needed to support the system. This is a desirable feature for thesystem since a low power footprint enables the use of a smaller batteryand also makes RF inductively coupled power more practical forapplication in the system. In another exemplary embodiment an integratedcircuit chip is operatively coupled with the sensor. As mentionedearlier, operative coupling may be direct or remote. The integratedcircuit may contain a data transmitter and/or processor. The benefit ofusing an integrated circuit is that it offers the capability of a datatransmitter, data processor, and/or processor/transmitter. In anotherexemplary embodiment the system further comprises a data transmittereither as part of an integrated circuit chip or as a standalonetransmitter that is operatively coupled with the sensor and transmitsusing one or several of the following communication methods:radiofrequency (RF), Bluetooth, WiFi, or other near-field communicationmeans. Another exemplary embodiment further comprises a receiver forreceiving sensor data from the sensor. The receiver may be disposedintracorporeally or extracorporeally. The receiver could process thesensor data and then transmit data to a display device which isconfigured to display the data to a physician or other caregiver. Asmentioned earlier any of the features described in exemplary embodimentsdisclosed herein may be used in combination with or substituted with oneor several other features disclosed in any of the other exemplaryembodiments disclosed herein.

FIG. 20 discloses an exemplary embodiment of a system for monitoringflow through a prosthesis, said system comprising: a prosthesis having alumen extending therethrough, the lumen configured for fluid flowtherethrough; and a sensor operatively coupled with the prosthesis, thesensor configured to sense a characteristic of the fluid flow and outputdata related to the fluid flow. In FIG. 20, any of the exemplaryembodiments of prostheses mentioned herein (object 52) are implantedinto a hollow conduit (object 51) in the body to preferably improve flowthrough 51. 52 optionally may be coupled with an integrated circuit(object 54), a power source (object 53) and/or a transmitter (object55). The sensor data is transmitted wirelessly (59 a) to an externalreceiver (56). 56 contains a processor to process the raw data into asignal that is transmitted wirelessly (59 b) optionally to an externalsite for storage (57) and ultimately to a display monitor or device (58)which can be read by a clinician or other care provider.

In another aspect of the present invention, a method for monitoring flowthrough a hollow conduit such as a prosthesis is disclosed. Any of theexemplary embodiments of this aspect of the invention may use one orseveral of the exemplary embodiments of the fluid monitoring prosthesisdisclosed herein. This method comprises providing a prosthesis having alumen therethrough and a sensor coupled to the prosthesis; coupling theprosthesis to a fluid path in a patient so that fluid flows through theprosthesis; sensing the fluid flow with a sensor transmitting datarepresentative of the sensed fluid flow to a receiver disposedextracorporeally relative to the patient and outputting the data. In anexemplary embodiment the prosthesis is a prosthetic vascular graft suchas one made from a material like PTFE, ePTFE, polyester, polyethyleneterephthalate, nitinol, cobalt chromium alloy, stainless steel,bioabsorbable polymers such as PGA, PLA, etc., or another suitableflexible and/or expandable material. The prosthetic vascular graft maybe a graft, stent, or stent-graft. The fluid path also may be comprisedof a blood flow path, urinary flow path, cerebrospinal flow path, lymphflow path, or flow path of another bodily fluid. Transmitting the datamay comprise sending the data wirelessly to another device or systemwhich is operatively coupled to the sensor.

The tubular prosthesis described above is used in an anastomosisprocedure to replace or bypass a section of damaged or stenotic bloodvessel, as is known to those skilled in the art. The procedure ofimplanting a tubular prosthesis in order to bypass a lesion in a singlevessel (FIG. 24), the original vessel being depicted by object 64 andthe prosthesis by object 63, and the orifices of the tubular prosthesisbeing attached by end-to-side anastomoses. In FIG. 28, the utilizationof a tubular prosthesis (object 79) to connect two distinct vessels(objects 80 and 81) is described. In order to implant the tubularprosthesis, a healthy section of blood vessel is selected adjacent tothe damaged blood vessel. The vessel is appropriately accessed and anaperture is formed in the healthy section of distal blood vessel. Theaperture is formed to appropriately accommodate the distal orifice ofthe tubular prosthesis. The distal end of the tubular prosthesis is thenjoined appropriately by the medical practitioner to the aperture such asby suturing the ends together, stapling or gluing them together. Asubcutaneous conduit or tunnel is then created in the adjacent tissue inorder to accommodate the body of the tubular prosthesis. The step offorming an aperture is repeated in a second section of healthy bloodvessel at the proximal end of the damaged section of blood vessel or theaperture may be created in an altogether different blood vessel. Onceagain, an appropriately sized shaped aperture is created to accommodatethe proximal end of the tubular prosthesis. The proximal end of thetubular prosthesis is then joined to this aperture using similartechniques as previously described. During the implantation procedure,blood is typically prevented from passing through the blood vessel beingoperated on; but, once the proximal and distal ends are appropriatelyattached, blood is allowed to pass through the blood vessel and into thetubular prosthesis.

In another exemplary embodiment, the method whereby the tubularprosthesis may be used in a procedure where a venous cuff is employed byone skilled in the art is described. In this method, depicted in FIG.23, the distal orifice of the tubular prosthesis (object 60) is attachedto the proximal orifice of an autograft or allograft (object 61), suchas a saphenous or antecubital vein. The distal orifice of the autograftis then attached to the aperture created in the relevant vessel (object62). The proximal orifice of the tubular prosthesis is attached to thevessel providing fluid inflow. The distal anastomotic site is a knownarea of increased intimal hyperplasia and possible stenosis. Utilizing avenous cuff has been shown to reduce the amount of intimal hyperplasiaformation and stenosis formation, as described by Neville, et al. Eur JVasc Endovasc Surg. August 2012. It may prove advantageous to utilizethis method to not only reduce the likelihood of stenosis formation, butto also enable monitoring of the prosthetic. In another embodiment, thetubular prosthesis may also be attached to another synthetic orstem-cell derived graft, as needed.

In the reverse of the embodiment above, a method whereby an autograft orother synthetic is utilized as the main body of the bypass, repair orreplacement by one skilled in the art is described. In this method, thedistal orifice of the autograft or other synthetic graft such as ePTFE,or polyester grafts like Dacron, is attached to the proximal orifice ofthe tubular prosthesis. The distal orifice of the tubular prosthesis isthen attached via methods known by those skilled in the art to anaperture created in the relevant vessel. The proximal orifice of theautograft, allograft, xenograft or other synthetic or stem-cell derivedgraft is attached to the vessel providing fluid inflow. This methodallows for a minimization of immune response while allowing the tubularprosthesis to report data relating to the aforementioned parameters.

Transluminal stent-graft placement and other methods of device deliveryare well-known to those skilled in the art (see U.S. Pat. Nos.7,686,842, 8,034,096). Open surgical placement of a stent-graft deviceis also defined in U.S. Pat. No. 8,202,311. A method whereby a tubularprosthesis comprising a stent-graft, as described above, is capable ofbeing deployed in a similar manner by those skilled in the art will bebriefly described, and is depicted in FIG. 25. In FIG. 25 the vesselwhich has an aneurysm is depicted by object 68 and the aneurysmal sac isdepicted by object 67. The stent portion of the stent graft is depictedby object 65 and the graft portion by object 66. A sheath is introducedinto an appropriate vessel using known techniques such as a surgicalcutdown or a percutaneous procedure like the Seldinger technique, andthen advanced to the appropriate position, preferably over a guidewire.In the case of an aneurysm or rupture, an occlusion balloon catheter maybe advanced and deployed in order to control bleeding. Imagingmodalities may be used to size the required tubular prosthesis; this mayalso be accomplished via a calibration guidewire. Once appropriatelysized, the tubular prosthesis is loaded onto the distal tip of a sheathor catheter and delivered to the appropriate surgical site. In apreferred embodiment, the tubular prosthesis is mounted over a deliverycatheter which is then delivered to the target treatment site,preferably over a guidewire. An imaging modality may then be utilized toensure correct placement before deployment. The tubular prosthesis mayinclude a self-expanding stent which deploys upon retraction of aconstraining sheath therefrom, or the tubular prosthesis may include aballoon expandable stent which is deployed by a balloon or otherexpandable member on the delivery catheter. Full expansion of thestent-graft is assured by optional dilation with the aid of anexpandable member such as a balloon on the delivery catheter or anothercatheter which tacks also tacks the stent-graft into position. Animaging modality is once again utilized to ensure stent-graft patencywithout evidence of migration, vessel rupture, perigraft leak, ordissection.

In another embodiment, the method of deployment may involve a stent orstent-graft which is capable of self-expansion or self-deployment via anelectrical current being induced across the sensor which may be apiezoresistive element. For example, the piezoresistive element maygenerate a current which passes through the stent portion of the stentor stent-graft, resulting in heating of the stent thereby elevating thestent temperature above a transition temperature which results inself-expansion of the stent. Shape memory alloys such as nickel titaniumalloys are well known in the art and can be used in this embodiment. Thepiezoresistive element is capable of sensing pressure, among otherpreviously identified characteristics, and then transmitting this datavia a transmitter operatively coupled to the prosthesis to the medicalpractitioner and being preset for a particular amount of stress, thisembodiment would aid in the possible prevention of leaks, ruptures ordissections, or overexpansion of the stent-graft. In another method, anappropriate imaging modality may be utilized to ascertain the size ofthe relevant lumen. The piezoresistive element may then be programmed orpreset to demonstrate a particular amount of strain or stress. Themedical practitioner may then induce an appropriate electrical currentvia mechanisms known by those skilled in the art into the piezoresistiveelement. This would allow the piezoresistive element to aid inmaintaining the patency of the lumen and may help prevent leaks,ruptures, dissections, overexpansion, etc.

A method of deploying a tubular prosthesis in the form of a stent, asdefined by those skilled in the art and partially described by U.S. Pat.Nos. 8,551,156, 8,597,343, 8,579,958, etc., in order to monitorparameters regarding flow or occlusion is described. FIG. 26 depicts astent (object 70) which has been placed in a vessel (object 69). A stentmay be used to maintain patency of any hollow conduit within the body.Stents are typically positioned within the appropriate vessel or conduitand then expanded from within using a stent delivery balloon and/or anangioplasty balloon, as is known to those skilled in the art, or thestent may be a self-expanding stent which expands when a constraint isremoved, or when the stent is heated above a transition temperature. Asensor may be coupled to the stent to monitor flow through the stent.

In another embodiment, one orifice of the tubular prosthesis is placedtransluminally into a vessel, the other orifice is then attached toeither or the same vessel or another vessel via an end-to-end orend-to-side anastomosis. This utilization of a hybrid stent graft iswell known to one skilled in the art and is described by Tsagakis K etal. Ann Cardiothorac Surg, September 2013.

The tubular prosthesis described above may also be used in ananastomosis procedure to replace or bypass a section of damaged orstenotic ureteral vessel, as known to those skilled in the art. A methodof implanting a tubular prosthesis in order to bypass a lesion in asingle vessel or to connect two distinct vessels to enhance the drainageof urine is described. In order to implant the tubular prosthesis, ahealthy section of ureteral vessel is selected adjacent to the damagedvessel. The vessel is appropriately accessed and an aperture is formedin the healthy section of distal ureter. The aperture is formed toappropriately accommodate the distal orifice of the tubular prosthesis.The distal end of the tubular prosthesis is then joined appropriately bythe medical practitioner to the aperture using methods known in the artsuch as by suturing, stapling, gluing, etc. A conduit or tunnel is thencreated in the adjacent tissue to accommodate and secure the body of thetubular prosthesis. The step of forming an aperture is repeated in asecond section of healthy ureter at the proximal end of the damagedsection of ureter or the aperture may be created in an altogetherdifferent hollow conduit, such as the contralateral ureter, bladder,urethra, colon or external container with a transcutaneous conduit. Onceagain, an appropriately sized and shaped aperture is created toaccommodate the proximal end of the tubular prosthesis. The proximal endof the tubular prosthesis is then joined to this aperture similarly asthe distal end. During the implantation procedure, urine is typicallyprevented from passing through the ureter being operated on; but, oncethe proximal and distal ends are appropriately attached, urine isallowed to pass through the blood vessel and into the tubularprosthesis. An imaging modality will be used to ensure flow through thetubular prosthesis and lack of leaks, ruptures, dissections, etc.

In another embodiment, the tubular prosthesis described above may beused as a ureteral stent, designed to be placed within a patient'sureter to facilitate drainage from the patient's kidneys to the bladder,as described in U.S. Pat. No. 6,764,519. The method includes placementof a ureteral stent device in a ureter of a patient, as is known tothose skilled in the art.

In yet another embodiment, the tubular prosthesis described above may beused as a urethral stent (such as U.S. Pat. No. 5,681,274) designed tobe placed within a patient's urethra to facilitate drainage from orthrough the patient's kidney or bladder to the external environment. Themethod of deployment for a urethral stent is well known to those skilledin the art. In another embodiment, this stent may be biodegradable insuch a fashion that flow may be monitored temporarily. As the stentbiodegrades, the sensor would be expelled via the flow of urine.

In another embodiment, a tubular prosthesis as described above may beused as a urinary catheter, as described in U.S. Pat. No. 4,575,371. Inthis method, the urinary catheter is designed to be placed within anorifice residing within the bladder of an individual, as is known tothose skilled in the art. The tubular prosthesis would then act as aurinary catheter to facilitate drainage of urine from or through thepatient's bladder to an extracorporeal container.

An embodiment whereby the tubular prosthesis is utilized as atransjugular intrahepatic portosystemic shunt (TIPS); a method anddevice being described in U.S. Pat. No. 8,628,491. The method describedhere is useful for monitoring flow and/or occlusion parameters in asynthetic shunt between the portal vein from a hepatic vein. Thecreation of a transjugular intrahepatic portosystemic shunt is wellknown to those skilled in the art and allows blood to bypass the hepaticparenchyma responsible for elevated portal vein pressures and isdescribed here. After being sufficiently anesthetized, the patient'sright internal jugular vein is accessed and a catheter is advanced viathe superior vena cava, the right atrium, and inferior vena cava to theright hepatic vein. A sheath is then guided into the right hepatic vein.A large needle is then pushed through the wall of the hepatic vein intothe parenchyma anteroinferomedially in the expected direction of theright portal vein. When blood has been aspirated, an imaging modality isutilized to ensure access into the right portal vein. A guidewire isthen advanced into the main portal vein. An expandable member is placedover this wire and dilated creating a conduit between the hepatic systemand the portal system. A tubular prosthesis as described above, is thenplaced within the conduit and dilated forming the intrahepaticportosystemic shunt. If the patient is not suitable for a transluminaldelivery of the shunt, an open surgery may be performed by a surgeon,interventional radiologist or other trained medical professional. Inthis embodiment, apertures are created between both the right, left orcommon hepatic vein and the portal vein. A shunt is then created byattaching each orifice of the tubular prosthesis described above to itsrelevant aperture. Expansion of the stents in the stent-graft anchor theprosthesis in the desired position.

Another embodiment is a method whereby flow and/or occlusion parameters,pursuant to a liver resection or transplant by those skilled in the art,are monitored within the portal and hepatic systems via any of thetubular prostheses described above.

Another embodiment is a method whereby any of the tubular prosthesesdescribed above is employed as a cerebrospinal fluid shunt system forthe monitoring and treatment of hydrocephalus. The creation of acerebrospinal fluid shunt system is well known to those skilled in theart.

In another embodiment, any of the tubular prostheses disclosed herein isemployed as a drainage apparatus for cerebrospinal fluid (which maycontain blood) and is utilized as a method for the monitoring andtreatment of cerebral or spinal damage. In this method, the tubularprosthesis is to be implanted by one skilled in the art with an orificelocated at the site which is to be drained. The prosthesis may beinterrogated either continuously and/or at a series of predefined timepoints and/or on an ad hoc basis.

Another embodiment is a method whereby any of the tubular prosthesesdescribed herein is employed as a drainage apparatus during a surgicalprocedure. In this method, the prosthesis may be interrogated by oneskilled in the art for data either continuously and/or at a series ofpredetermined time points and/or on an ad hoc basis.

Yet another embodiment is a method whereby any of the tubular prosthesesis employed as a drainage apparatus post-surgical procedure. In thismethod, the tubular prosthesis is appropriately secured by one skilledin the art. The prosthesis may then be interrogated by one skilled inthe art for data either continuously and/or at a series of predeterminedtime points and/or on an ad hoc basis.

FIG. 29 discloses another exemplary embodiment wherein a method ofcoupling comprises slidably engaging the prosthesis over a native vesselor another prosthesis. In this method the tubular prosthesis is slidover the vessel to be monitored. This vessel may be any natural hollowconduit within the body or may be any autograft, allograft, xenograft,stem-cell derived or synthetic conduit which is being placed within thebody and may need to be monitored.

A method whereby the tubular prosthesis is monitored after theimplantation procedures described above is described herein. Afterplacement of the tubular prosthesis, correct placement may be assuredvia an imaging modality such as ultrasound or angiography or by allowingfluid to pass through the lumen. Prior to data acquisition the sensor ispreferably activated and paired with an enabled device. Datarequisitioned from the tubular prosthesis by the medical practitionercan then be reviewed. In a preferred embodiment, upon review of thesensed data, the medical practitioner can determine whether flow throughthe prosthesis is adequate. If the medical practitioner were to deem theflow adequate, he or she may continue to interrogate the device atpredetermined time intervals or shorten the time interval based onclinical judgment. If the medical practitioner were to deem the flowinadequate, he or she may perform one of several procedures; such as adilatation of the lesion and its surroundings with an expandable membersuch as a balloon angioplasty catheter, administration of a lytic agent,removal and replacement of the prosthesis or a procedure whereby thelesion is broken up and the resultant debris removed from the lumen,such as an embolectomy. These methods are depicted in FIG. 27, whereinobject 72 is the lesion as it may appear prior to intervention andobject 73 is the lesion post-intervention. In FIG. 27, the vessel isdepicted by object 74 and the lumen by object 75. The expandable memberis depicted in its closed configuration by object 77 and in its expandedconfiguration by object 78. In another embodiment, after review of thedata, the medical practitioner may deem it necessary to conductadditional diagnostic testing, such as an ultrasound, Dopplerultrasound, computer aided tomography scan (CAT), magnetic resonanceimaging (MRI), etc. Following a review of this data, the medicalpractitioner may choose to perform one of the procedures indicatedabove. In another embodiment, review of sensed data may take on a uniqueform. Data requisitioned from the sensor may be listened to as an audiofile; this is enabled by current data acquisition methods which canproduce a waveform audio format file (.wav file). The medicalpractitioner may choose to listen to the flow within the lumen anddetermine whether flow is adequate or an intervention may be necessary.In exemplary embodiments where the sensor includes a piezoresistiveelement, the piezoresistive element acts as a microphone picking upacoustic signals from within the lumen of the tubular prosthesis. Thiscan help the medical practitioner identify turbulence or stenosis. Inaddition, this method is not encumbered by signal interference as may beencountered when utilizing a stethoscope or ultrasound to acquireacoustic signals from the lumen of a prosthesis.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. For example, any of themedical procedures described above may be used in conjunction with anyof the prostheses disclosed herein in order to monitor flow.Furthermore, any of the features of one particular prosthesis maybe usedin conjunction with or substituted with another feature described in anyof the embodiments of prostheses described herein. It should beunderstood that various alternatives to the embodiments of the inventiondescribed herein may be employed in practicing the invention. It isintended that the following claims define the scope of the invention andthat methods and structures within the scope of these claims and theirequivalents be covered thereby.

What is claimed is:
 1. A prosthesis for monitoring a characteristic offlow, said prosthesis comprising: a first tubular prosthesis; a secondtubular prosthesis having a lumen extending therethrough, wherein thefirst tubular prosthesis is disposed over the second tubular prosthesis[thereby forming a pocket therebetween]; and a non-optical sensor fordetecting a characteristic of fluid flowing through the lumen of thesecond tubular prosthesis, wherein the sensor is disposed on either thefirst or the second tubular prosthesis [in the pocket, and], wherein thesensor is insulated from contact with fluid flowing through the lumenand is not encapsulated within a material forming either of the first orsecond tubular prosthesis.
 2. The prosthesis of claim 1, wherein theprosthesis for monitoring the characteristic of flow is a prostheticvascular graft.
 3. The prosthesis of claim 1, wherein the first tubularprosthesis or the second tubular prosthesis is a tubular prostheticvascular graft.
 4. The prosthesis of claim 1, wherein the non-opticalsensor comprises a first non-optical sensor provided near one end of thesecond tubular prosthesis and a second non-optical sensor provided nearan opposite end of the second tubular prosthesis.
 5. The prosthesis ofclaim 1, wherein the first tubular prosthesis or the second tubularprosthesis is formed primarily from polyethylene terephthalate,polyester or ePTFE.
 6. The prosthesis of claim 1, wherein the firsttubular prosthesis or the second tubular prosthesis is a stent.
 7. Theprosthesis of claim 1, wherein the first tubular prosthesis or thesecond tubular prosthesis is a stent-graft.
 8. The prosthesis of claim1, wherein the first tubular prosthesis is fixedly attached to thesecond tubular prosthesis.
 9. The prosthesis of claim 1, wherein thefirst tubular prosthesis is integral with the second tubular prosthesis.10. The prosthesis of claim 1, wherein the first tubular prosthesis issintered to the second tubular prosthesis.
 11. The prosthesis of claim1, wherein the first tubular prosthesis is sutured to the second tubularprosthesis.
 12. The prosthesis of claim 1, wherein the first tubularprosthesis has a first length and the second tubular prosthesis has asecond length substantially the same as the first length.
 13. Theprosthesis of claim 1, wherein the first tubular prosthesis has a firstlength and the second tubular prosthesis has a second length shorterthan the first length.
 14. The prosthesis of claim 1, wherein the firsttubular prosthesis has a first length and the second tubular prosthesishas a second length longer than the first length.
 15. The prosthesis ofclaim 1, wherein the first tubular prosthesis is discrete from thesecond tubular prosthesis.
 16. The prosthesis of claim 1, wherein thesensor comprises a piezoelectric sensor or a Doppler sensor.
 17. Theprosthesis of claim 1, wherein the sensor detects thermal properties ofthe fluid flow, stress, strain, or pressure exerted on the first or thesecond tubular prosthesis by the fluid flow.
 18. The prosthesis of claim1, wherein the characteristic sensed by the sensor comprises velocity orflow rate of the fluid flow, or occlusion, degree of occlusion,stenosis, or degree of stenosis in the lumen.
 19. The prosthesis ofclaim 18, wherein the velocity is determined indirectly from the sensedcharacteristic.
 20. The prosthesis of claim 18, wherein the velocity isdetermined directly from the sensed characteristic.
 21. The prosthesisof claim 1, wherein the sensor is disposed circumferentially around thefirst and/or the second tubular prosthesis.
 22. The prosthesis of claim21, wherein the first or the second tubular prosthesis has alongitudinal axis, and wherein the sensor is orthogonal to thelongitudinal axis.
 23. The prosthesis of claim 1, wherein the sensorcomprises a plurality of sensors disposed circumferentially around thefirst and/or the second tubular prosthesis.
 24. The prosthesis of claim1, wherein the sensor comprises a plurality of discrete sensorscircumferentially disposed around the first and/or the second tubularprosthesis, and wherein the plurality of discrete sensors are disposedin a common plane.
 25. The prosthesis of claim 1, wherein the sensorcomprises a plurality of discrete sensors disposed axially along thefirst and/or the second tubular prosthesis.
 26. The prosthesis of claim25, wherein the plurality of discrete sensors are disposed substantiallyparallel to a longitudinal axis of the first and/or the second tubularprosthesis.
 27. The prosthesis of claim 1, wherein the sensor comprisesfirst and second annular bands circumferentially disposed around thefirst and/or the second tubular prosthesis, and wherein the firstannular band is axially separated from the second annular band.
 28. Theprosthesis of claim 27, wherein the first or the second annular bandforms a closed loop.
 29. The prosthesis of claim 1, wherein the sensorcomprises a plurality of elongated sensors, the plurality of elongatedsensors axially oriented along the first and/or the second tubularprosthesis.
 30. The prosthesis of claim 1, wherein the sensor isconfigured to capture a plurality of characteristics of the fluid flowin the lumen.
 31. The prosthesis of claim 1, wherein the sensorcomprises a plurality of sensors disposed on the first and/or the secondtubular prosthesis.
 32. The prosthesis of claim 31, wherein theplurality of sensors comprise a first sensor and a second sensor,wherein the first sensor is configured to capture a first characteristicof the fluid flow in the lumen, and wherein the second sensor isconfigured to capture a second characteristic of the fluid flow in thelumen.
 33. The prosthesis of claim 32, wherein the first characteristicis different than the second characteristic.
 34. The prosthesis of claim32, wherein the first characteristic and the second characteristics areportions of a single signal.
 35. The prosthesis of claim 32, wherein thefirst sensor is disposed in a first orientation relative to the first orthe second tubular prosthesis, and wherein the second sensor is disposedin a second orientation relative to the first or the second tubularprosthesis, and wherein the first orientation is different than thesecond orientation.
 36. The prosthesis of claim 31, wherein theplurality of sensors are helically disposed around the first or thesecond tubular prosthesis.
 37. The prosthesis of claim 1, wherein thefirst or the second tubular prosthesis has a longitudinal axis, andwherein the sensor is disposed substantially parallel to thelongitudinal axis.
 38. The prosthesis of claim 1, wherein the first orthe second tubular prosthesis has a longitudinal axis, and wherein thesensor is disposed transverse to the longitudinal axis.
 39. Theprosthesis of claim 1, wherein the sensor comprises a plurality ofundulating elongated elements disposed over the first and/or the secondtubular prosthesis.
 40. The prosthesis of claim 39, wherein the sensorhas a collapsed configuration sized for delivery of the sensor and anexpanded configuration adapted to substantially match an anatomy inwhich the sensor is deployed, and wherein in the expanded configurationthe sensor forms a closed annular band.
 41. The prosthesis of claim 1,wherein the sensor is disposed circumferentially around the first or thesecond tubular prosthesis to form a closed annular band therearound. 42.The prosthesis of claim 1, wherein the sensor is partially disposedcircumferentially around the first or the second tubular prosthesis toform an open annular band therearound.
 43. A system for monitoring flowthrough a prosthesis, said system comprising: a prosthesis having alumen extending therethrough, the lumen configured for fluid flowtherethrough; and a sensor operatively coupled with the prosthesis, thesensor configured to sense a characteristic of the fluid flow and outputdata related to the fluid flow.
 44. The system of claim 43, furthercomprising a wireless transmitter for transmitting the data from thesensor to a remote position.
 45. The system of claim 43, furthercomprising a display device operatively coupled with the sensor, thedisplay device configured to display the output data.
 46. The system ofclaim 43, further comprising a processor configured to process theoutput data.
 47. The system of claim 43, further comprising a powersource for providing power to the system.
 48. The system of claim 47,wherein the power source comprises a battery.
 49. The system of claim43, wherein the sensor does not require power to be actively suppliedthereto in order to sense the fluid flow and output data related to thefluid flow.
 50. The system of claim 43, further comprising an integratedcircuit chip operatively coupled with the sensor.
 51. The system ofclaim 50, wherein the integrated circuit chip does not contain aprocessor.
 52. The system of claim 50, wherein the integrated circuitchip comprises a data transmitter.
 53. The system of claim 52, whereinthe data transmitter transmits using at least one of radiofrequency,Bluetooth, internet, or near field communication means.
 54. The systemof claim 43, further comprising a receiver for receiving the data. 55.The system of claim 54, wherein the receiver is an intracorporeal or anextracorporeal device.
 56. The system of claim 54, wherein the receiverprocesses the data prior to transmission of the data to a display deviceconfigured to display the data to a physician or other caregiver.
 57. Aprosthesis for monitoring flow, said prosthesis comprising: a firsttubular prosthesis having a lumen extending therethrough; a sensorcoupled to the first tubular prosthesis, wherein the sensor isconfigured to sense fluid flow through the lumen; and a layer ofmaterial disposed over the sensor and sealingly coupled to a surface ofthe first tubular prosthesis thereby encapsulating the sensor such thatthe sensor is insulated from contact with fluid flowing through thelumen.
 58. The prosthesis of claim 57, wherein the first tubularprosthesis is a prosthetic vascular graft.
 59. The prosthesis of claim57, wherein the fluid is blood and the fluid flow is blood flow throughthe prosthesis.
 60. The prosthesis of claim 57, wherein the firsttubular prosthesis is formed primarily from polyethylene terephthalate,polyester, or ePTFE.
 61. The prosthesis of claim 57, wherein the firsttubular prosthesis is a stent.
 62. The prosthesis of claim 57, whereinthe first tubular prosthesis is a stent-graft.
 63. The prosthesis ofclaim 57, wherein the sensor is coupled to an inner surface of the firsttubular prosthesis.
 64. The prosthesis of claim 57, wherein the sensoris coupled to an outer surface of the first tubular prosthesis.
 65. Theprosthesis of claim 57, wherein the layer of material is a patch. 66.The prosthesis of claim 57, wherein the layer of material is sintered,adhesively coupled, sutured, or stapled to the first tubular prosthesis.67. A method for monitoring flow through a prosthesis, said methodcomprising: providing a prosthesis having a lumen therethrough and asensor coupled to the prosthesis; coupling the prosthesis to a fluidpath in a patient so that fluid flows through the prosthesis; sensing acharacteristic of the fluid flow through the lumen with the sensor;transmitting data representative of the sensed fluid flow to a receiverdisposed extracorporeally relative to the patient; and outputting thedata.
 68. The method of claim 67, wherein the prosthesis is a prostheticvascular graft.
 69. The method of claim 67, wherein the prosthesis is astent or a stent-graft.
 70. The method of claim 67, wherein the fluidpath comprises a blood flow path.
 71. The method of claim 67, whereintransmitting the data comprises wirelessly transmitting the data. 72.The method of claim 67, further comprising: reviewing the sensed data;determining whether flow through the prosthesis is adequate based on thesensed data; and performing a blockage clearing procedure on theprosthesis if the flow is inadequate.
 73. The method of claim 72,wherein the blockage clearing procedure comprises an angioplasty,atherectomy or administration of a thrombolytic agent.
 74. The method ofclaim 67, further comprising indicating the necessity of additionaldiagnostic testing of the prosthesis.
 75. The method of claim 67,wherein the data comprises an acoustic signal.
 76. The method of claim67, further comprising pairing the prosthesis with an external device.77. The method of claim 67, wherein the coupling comprises forming ananastomosis between a proximal end or a distal end of the prosthesis andthe fluid path.
 78. The method of claim 67, wherein the couplingcomprises positioning the prosthesis between a native vessel and anothergraft or a second native vessel.
 79. The method of claim 67, wherein thecoupling comprises positioning the prosthesis between ends of a nativevessel.
 80. The method of claim 67, wherein the coupling comprisescoupling an end of the prosthesis to a side of a native vessel or nativeconduit.
 81. The method of claim 67, wherein the coupling comprisesslidably engaging the prosthesis over a native vessel or anotherprosthesis.
 82. The method of claim 67, wherein the fluid flow is bloodflow.
 83. The method of claim 67, wherein the fluid flow is urine flow,cerebrospinal fluid flow or other non-blood flow.
 84. The method ofclaim 67, wherein outputting the data comprises sending the data to abedside monitor, the bedside monitor optionally coupled to the Internet.85. The method of claim 67, further comprising an enabled device, theenabled device interrogating the prosthesis.
 86. The method of claim 85,wherein the enabled device comprises a pacemaker, an implantable device,bedside monitor, a glucose meter, a blood pressure meter, a smart phone,a smart watch, or an Internet connected device.
 87. The method of claim67, further comprising inductively providing power to the prosthesis.